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Full text of "Phytotron manual."

l»t, 1 Agriculture 



Canada 

Research Direction generate 
Branch de la recherche 



Technical Bulletin 1 988-4E 




Phytotron manual 



AGRICULTURE CANADA 
CCDE 88/03/10 NO. 



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Phytotron manual 



A.M. HARPER and D.W.A. ROBERTS 
Research Station, Agriculture Canada 
Lethbridge, Alberta 

Technical Bulletin 1988-4E 

Lethbridge Research Station Contribution No. 13 



Research Branch 
Agriculture Canada 
1988 



Copies of this publication are available from 

Dr. K.W. May 

Chairman, Phytotron Committee 

Cereal Crop Science Section 

Research Station 

Research Branch, Agriculture Canada 

Lethbridge, Alberta 

T1J4B1 

Published by Research Program Service 

© Minister of Supply and Services Canada 1988 
Cat. No.: A54-8/1988-4E 
ISBN: 0-662-15936-5 



cover 



The dots on the map represent Agriculture 
Canada research establishments. 



CONTENTS 

Page 

FOREWORD i 

SUMMARY/ RESUME ii 

INTRODUCTION 1 

FACILITIES 2 

Plant growth cabinets 2 

Plant growth rooms 3 

Greenhouses 3 

Controlled temperature rooms with limited light 4 

Headerhouse facilities 5 

PLANS OF PHYTOTRON AREA 6 

BASIC CONSIDERATIONS FOR CONTROLLED ENVIRONMENTS 7 

Benefits of controlled environments 7 

Refrigeration systems 8 

Temperature measurement 11 

Light 12 

Humidity 14 

ENVIRONMENTAL CONDITIONS 16 

Cold rooms 16 

Plant growth cabinets and rooms 16 

Introduction 17 

Temperature 17 

Light 23 

Humidity 23 

Air movement 23 

Watering 23 

Containers 27 

Nutrition and media 27 

Carbon dioxide 28 

Other gases 29 

Diseases and pests 29 

MANAGEMENT OF FACILITIES 33 

GUIDELINES FOR REPORTING PHYTOTRON EXPERIMENTS 34 

Equipment 34 

Temperature 34 

Light 3 5 

Relative humidity 35 

Carbon dioxide 35 

Air movement 36 

Containers, media, and nutrients 36 

REFERENCES AND SUPPLEMENTARY READING 37 



APPENDICES Page 

1. Summary of responsibilities 41 

2. Plant growth rooms 42 

3. Plant growth room benches 43 

4. Experimental rooms with limited light 44 

5. Phytotron program form 45 

6. Phytotron work order form 46 

7. Shut down and program change reguest form 47 

8. Preventative maintenance form 48 

9. Climatic data for Lethbridge 49 

A. Air temperature 

B. Frost data 

C. Soil temperature 

D. Degree days 

E. Precipitation 

F. Probability of growing season rainfall 

G. Sunshine 

10. Standard abbreviations 52 

11. Conversion factors 53 

12. Cornell mix 54 

13. Hoagland's solution 54 

14. Conversion of light units 55 



1 - 



FOREWORD 



This publication was written primarily to provide information about the 
Lethbridge Research Station Phytotron for new staff members. The 
publication also provides an overview of some of the problems with 
controlling environmental factors in the Phytotron. These problems need 
to be considered by all scientists when interpreting the results of their 
Phytotron experiments. 

Many scientists, engineers, architects, and administrators interested in 
planning new Phytotrons have visited the Lethbridge Research Station 
Phytotron and many have requested the type of information presented in 
this publication. 

The authors were on the planning committee for the Lethbridge Research 
Station Phytotron and have been involved with it since the start of its 
operation in 1976. Dr. A. M. Harper, an entomologist, was Chairman of 
the Phytotron Committee and managed the Phytotron and the preceding 
greenhouse and growth chamber operations from 1970-1986. Dr. D. W. A. 
Roberts, a plant physiologist, was Chairman of the Controlled Temperature 
Rooms Committee and a member of the Phytotron Committee from 1970-1987, 
and was instrumental in having the first plant growth cabinets constructed 
at the Research Station in the 1950 's. 

Several books have been written on Phytotrons and their authors have 
discussed in detail the problems they have encountered. Consequently, 
the effects of radiant energy on the aerial parts of plants have been 
well documented. We have only briefly summarized this subject area. 
Since one of the interests at Lethbridge has been the area of cold 
hardiness and growth at low temperatures, especially of cereals, and 
since the problems that have been encountered in this area have not been 
adequately covered by other authors, these subjects are covered in detail 
in this publication. Our experiences should be valuable to researchers 
working under conditions where similar but much less pronounced problems 
are to be expected. 



- 11 - 



SUMMARY 



Plans and physical features of the Phytotron at the Agriculture Canada 
Research Station, Lethbridge, Alberta, are presented, with information on 
its operation and management. The advantages and uses of the Phytotron 
and its limitations are discussed, particularly the accurate control of 
environmental factors. Guidelines for reporting Phytotron experiments 
are given and references and supplementary reading are listed. 



RESUME 



Le manuel contient les plans et les caracteristiques du phytotron de la 
station federale de recherches agricoles de Lethbridge de meme que des 
renseignements concernant son fonctionnement et sa gestion. On y discute 
de ses avantages et de ses utilisations et, en particulier, du controle 
precis des facteurs ambiants. On y trouve enfin des lignes directrices 
sur la fagon de preparer les rapports sur les experiences avec le phytotron 
ainsi que des references et une liste de lectures supplement aires. 



INTRODUCTION 

The Phytotron is a system of controlled environment facilities designed 
and operated for investigating relationships between plants and their 
environment. In the Phytotron several physical parameters of the 
environment including light quality and intensity, day length, air 
temperature, humidity, plant nutrition, and concentration of gases can be 
controlled. 

Because the Phytotron accelerates many phases of agricultural research, 
results can be obtained several times faster than in the field or 
greenhouse. A Phytotron can be used to obtain accurate knowledge of 
plant reactions to environmental factors. This information is difficult 
to obtain in the field where these factors are variable and almost 
uncontrollable . 

Phytotrons have been useful for studying and developing new varieties of 
crops that have a short growing season, are winter hardy, drought 
tolerant, or disease or insect resistant. They have also been valuable 
for studying plant physiology; insect and disease biology, development, 
and control; denitrif ication by soil organisms; plant nutrition; movement 
of nutrients, salts, and water in the soil; and the biology, growth, and 
control of terrestrial and aquatic weeds. 

The Phytotron at Lethbridge Research Station was opened in 1976 and was 
an expansion of eight greenhouses and 16 growth cabinets that were 
constructed locally or were purchased between 1957 and 1970. The present 
Phytotron consists of 67 growth cabinets, 23 growth rooms, and 10 
greenhouses. 

In addition, there is a series of 22 controlled temperature rooms with 
limited light that are used in conjunction with the Phytotron. The 
Research Station also has extensive controlled environment facilities for 
rearing and studying insects, and for studying animal parasites on both 
small and large animals. 

The Phytotron is available to scientists at the Research Station, 
visiting scientists, Post-doctorate Fellows, and graduate students 
working with Research Station scientists. 



- 2 - 

FACILITIES 

Plant growth cabinets 

There are 67 plant growth cabinets in the Phytotron of which 11 are 
0.65 m 2 in growth area, 6 are 1.40 m 2 , 2 are 1.67 m 2 , and 48 are 
3.35 m 2 . All the 0.65 m 2 cabinets are a reach-in type with only one 
door. The 1.4 m 2 cabinets are a reach-in type with two doors on one 
side, the 1.67 m 2 cabinets are reach-in types with one door on each 
side of the cabinet, and 45 of the 3.35 m 2 cabinets are reach-in types 
with two doors on each side. Three of the 3.35 m 2 cabinets are a 
walk-in type with a vestibule on one side which gives access to the plant 
growth area from only the one side. 

Two of the 3.35 m 2 cabinets have high ceilings (2.4 m) for growing tall 
crops such as corn. Five of the 3.35 m 2 cabinets have humidity 
control. One of these cabinets has humidif ication by steam and spray 
nozzles, and four have humidif ication by spray only. Four of the five 
cabinets have refrigeration-reheat dehumidif ication and the other cabinet 
can be fitted with a chemical dehumidif er. Two of the 1.40 m 2 cabinets 
are gas-tight, with gas ports, for studies with carbon dioxide or other 
gases. Each of the 0.65 m 2 growth cabinets and nine of the older 3.35 m 2 
cabinets have air-cooled condensing units and are completely independent. 
The other cabinets are independent except for cooling water for the 
water-cooled condensing units. Each growth cabinet has a shut-off valve 
for the cooling water so that the unit can be repaired without affecting 
other units. The cooling water system is in segments so that only one or 
a few units need to be closed down to repair a breakdown in one of the 
lateral lines. If the entire system fails, units can be kept operating 
by connecting them directly to the domestic water supply. 

The cabinets maintain accurate air temperatures (+ 0.5°C) in the range of 
-10 to 40°C, 5 to 40°C, or 10 to 40°C. The 13 cabinets that operate from 
-10 to 40°C have dual evaporators. Each cabinet has or will soon have an 
electronic programmer for setting and maintaining all programs. The 
cabinets can be programmed and monitored at the cabinet or at a central 
computer. 

One special area of the Phytotron is the Disease-Vector Laboratory where 
there are three rooms. One room contains seven 0.65 m 2 cabinets, one 
room contains four 0.65 m 2 cabinets, and the third room is an examination 
and transfer room. The cabinets are used for maintaining cultures and 
conducting experiments with insects and mites that transmit plant 
diseases. The plants in the cabinets are watered by a glove-sleeve 
insert in the locked door, and only the scientist and the technician 
working with the disease and insects or mites have access to the 
cabinet. When the plants are to be changed the cabinet is disconnected 
and moved to the examination room where the vectors are transferred to 
new plants. The old plants and all the debris are placed in plastic bags 
in the room and are discarded. The room is then thoroughly cleaned and 
the bench top washed with alcohol. During more than 10 years of 
operation no areas of the Phytotron have become infested from the 
disease-vector area. 



- 3 - 



Plant growth rooms 

There are 23 plant growth rooms with 45 plant growth beds that vary in 
size from 5.5 to 7.3 m 2 . The total room area is 602 m 2 of which the 
total plant growth area is 315 m 2 . The plant growth area constitutes 
51% of the total room area, and the aisles, which give ready access to 
the plant growth area, take up the other 49% of the room area. All 
refrigeration, heating, programming, and other equipment are in service 
corridors that are adjacent to but completely removed from the plant 
growth rooms . 

The service corridors contain nearly all the services that are needed in 
the rooms or by the machinery, such as electricity, compressed air, 
distilled water, demineralized water, and water from the community water 
supply. In our building the service corridor is the return duct for the 
building air conditioning. For this reason, the natural gas pipes are in 
the plant growth rooms as it is illegal to have them in the service 
corridor. The service corridor is also large enough to permit ready 
access to all machinery and removal of any part of the equipment used to 
condition the environment in the plant growth rooms. 

Each room is completely independent except for cooling water. All rooms 
are now controlled by electronic programmers or will soon be fitted with 
them. 

Most of the growth beds are approximately 1.4 m wide by 5.0 m long and 
many have access from both sides. The facilities were designed so that 
researchers would not have to reach more than 0.7 m to pick up or examine 
a pot or plant. 

Nineteen of the plant growth rooms are 2.4 m high. Four rooms, each with 
two plant growth areas, are 3 m high to permit normal growth of tall 
crops such as corn, and for the study of soils where plants are grown to 
maturity in large containers with a soil depth of 1 to 1.5 m. One room 
has a specially reinforced floor to withstand the weight of large amounts 
of soil. 

Tanks for controlling soil and air temperatures separately are available 
in four growth rooms. The soil temperature is controlled in narrow tanks 
by temperature-controlled water in which the pots are almost fully 
immersed. Air around the plants is controlled by the vertical movement 
of air from growth benches beneath the tanks. The plumbing for the soil 
temperature control can be readily removed and the beds can be used as 
normal plant growth beds. 



Greenhouses 

There are 10 greenhouses with 45 compartments and a total area of 1950 m 2 
Greenhouses are single-glazed, and each compartment has supplementary 
heating, lighting, and cooling with evaporative coolers. One greenhouse 
compartment has an electronic controller that controls the temperature 
more accurately than in the greenhouses with thermostats only. It opens 



- 4 - 



and closes the vents and controls the supplementary heating, cooling, and 
lighting. During the summer some of the greenhouses are shaded with 
metal blinds, and some with whitewash. None of the greenhouses is cooled 
by mechanical refrigeration because of the cost. The heating system is 
adequate to maintain the required temperature for plants when the outside 
temperature is at -40°C. 

Benches in all greenhouses are metal and all floors are concrete. When 
high humidity is needed in a greenhouse, water is sprayed on the floor 
several times a day, or electrical humidifiers are placed in the 
compartment. Metal benches and concrete floors are used for cleanliness 
and to make the control of insects, mites, and diseases easier. 



Controlled temperature rooms with limited light 

Associated with the Phytotron are 23 rooms with controlled temperatures 
and limited light. (See Appendix 4 for room temperatures and dimensions.) 

Twelve of these rooms are maintained at constant predetermined 
temperatures and divided equally into two groups. One group usually 
contains rooms at 25, 20, 15, 10, 5°C, and a spare. The spare room is 
used at various temperatures usually near the freezing point with the 
proviso that if one of the other rooms breaks down the scientist using 
the spare room must vacate it immediately. The spare room is then set at 
the temperature of the room that failed and maintained there permanently 
or at least until repairs are made. Often the room that failed becomes 
the new spare room. Rooms in the other group are run at 0.7 to 0.8, -5, 
-10, -15, -20°C, and a programmable low temperature. One room is run at 
0.7 to 0.8°C instead of 0°C to avoid freezing of exposed moist soil or 
vermiculite as explained later in the section on cold rooms. These rooms 
require frequent defrosting and are operated with defrosts every 4 
hours. The programmable low temperature room is used for studies on low 
temperature pathogens (snow molds). It has a programmer that permits 
gradual controlled lowering of air temperature and its evaporator is 
designed to reduce the frequency of defrosting. 

One cold room provides extra cold storage at -20°C and two others provide 
storage at -40°C. A third room at -40°C is reserved for storage of 
pesticide-laden material from the field that is awaiting chemical 
analysis. 

Two rooms are designed and operated for vegetable storage at temperatures 
just above freezing. These rooms have additive humidity control (steam 
generators). With the changing research program these rooms are now 
operated at 1 and -10°C (+ 0.5°C) and are used in a program to select 
cold-resistant lines of winter wheat. This change illustrates the 
possibilities of adapting a controlled temperature room facility to 
changing research requirements. 



- 5 - 



Three other rooms are operated just above the freezing point (4 to 5°C) 
for storage of insect-damaged plant material and diseased plants. One of 
these rooms is used for diseased potato storage and has additive humidity 
control (steam generator). 

One programmed cold room is used to freeze plants in connection with 
studies on hardiness. It has an evaporator which is designed to provide 
long periods (4-5 days) between defrosts at sub-zero temperatures rather 
than the 4 hours between defrosts in the 12 temperature rooms described 
above. The cold room with the long period between defrosts does not 
provide temperature control as accurate as in rooms with the short time 
between defrosts. 

Finally, there is a seed storage room which is run at 5°C. This room has 
a dryer that keeps the relative humidity below 20%. It is used only for 
long-term storage of genetic stocks. All seed material is inspected for 
pests before it is placed in the room and yearly thereafter. Infested 
material found in the room is removed and treated to destroy the pests 
before it is returned to the room. 



Headerhouse facilities 

The following rooms and areas are in a headerhouse adjoining the main 
portion of our Phytotron and are used in conjunction with it: 

Vegetable research laboratory 

Plant physiology laboratory 

Insect and disease assessment laboratory 

Plant dissection, examination, and washing laboratory 

Eguipment and plant washing room 

Seed storage room (temperature and humidity controlled) 

Pesticide-laden plant storage room (-40°C) 

Garbage storage room (air-conditioned) 

Incinerator room 

Plant drying room (small and large dryers) 

Plant nutrient preparation room 

Pot and material storage rooms 

Plant spray room 

Fungicide, insecticide, and fumigant storage room 

Autoclave 

Soil and plant grinding room (with special dust removers) 

Soil storage and mixing rooms 

Storage room for special soils in containers 

Equipment maintenance room 

Potting, seeding, and examination benches 

Service trucks can be driven into the main area of the headerhouse to 
load and unload materials. Soil is loaded into the soil bins through 
doors to the exterior that open into each bin. 



- 6 - 



PLANS OF PHYTOTRON AREA 




A= standard cabinet (5 to 40 °C) 
B= growth bench (5 to 40°C) 
C= temperature room, 

limited light (-40 to 40°C) 
F = air-cooled small cabinets in 

disease-vector room (5 to 40°C) 
LT= low temperature cabinet (-10 to 40°C) 
RR= controlled humidity cabinet 

(refrigeration reheat) (5 to 40 C) 



HC = high ceiling cabinet (5 to 40°C) 
V « vestibule (5 to 40"C) 
VLT = vestibule, low temperature 
(-10 to 40°C) 



MAIN FLOOR 
SERVICE WING 



38 m 




n 



^ ^55^ 



j" 



B = growth bench 
(5 to 40°C) 



BASEMENT 
SERVICE WING 



- 7 - 

BASIC CONSIDERATIONS FOR CONTROLLED ENVIRONMENTS 

Benefits of controlled environments 

The introduction long ago of the greenhouse started freeing the plant 
scientist from the vagaries of the field. In the last 50 years in Canada 
the development of completely artificial environments for growing plants 
has provided a quantum leap forward in this direction. 

The first, but probably not the most important, advantage of the Phytotron 
is its capacity for the production of crops on a year-round basis in 
northern climates. Furthermore, uniform materials for biochemical, 
physiological, entomological, pathological, and genetic studies can be 
produced so that experiments can be planned and spread over the entire 
year, as desired, to utilize staff efficiently. This stands in strong 
contrast to the greenhouse where wintertime production of plant material 
is often limited by short day lengths and low light intensities. 
Greenhouse production in summer requires supplementary cooling. 

In a Phytotron it is possible to adjust conditions so that hybridization 
can be done at any time during the year and good seed set can be obtained 
for early generations of a breeding program. This shortens the duration 
of breeding programs by several years. Consequently, a new generation may 
be started very soon after the parent plants set seed. In this way three 
generations per year of cereals and six generations of faba beans can be 
obtained. 

Controlled environments are advantageous for pathological studies since 
environmental conditions often control infestation and may alter 
resistance, such as with cereal bunt or disease expression in ring rot of 
potatoes. With controlled environment facilities it is possible to 
identify the environmental factors influencing the changes in resistance 
or disease expression. 

The greatest advantage to be gained from the use of the Phytotron is the 
control of growing conditions. Controlled environment facilities have, 
for example, made possible a much more accurate picture of the conditions 
that affect cold hardening of wheat in the field. The use of such 
facilities has made it clear that there is more to temperature effects 
than just increased hardiness with lowered temperature within specified 
limits. These facilities have made possible an explanation of why 
killing occurs in late winter and early spring and have permitted the 
development of a technique for testing hardiness which can be used to 
select for resistance to such killing. 

Detailed work on the genetics of cold hardiness in wheat is an example of 
a study that would be almost impossible without controlled environment 
facilities for hardening and hardiness testing. In the field, 
winterkilling is variable from one part of a field to another and is 
often all or none. Many tests are lost because of a lack of differential 
kill. Winters are sufficiently variable and unpredictable that it is 
impossible to select a site that will give consistent winterkilling due 
to low temperatures. Furthermore, in the field winterkilling may be 



- 8 - 



caused by disease. Differential kills on tender material for genetic 
studies require short mild winters, whereas long cold winters are 
required for differential kills on very hardy materials. Such places in 
the field are usually widely separated, often by hundreds of miles. 

In order to gain maximum advantages from the use of a Phytotron, its 
operation and limitations must be understood. This understanding is 
essential for the proper interpretation of experimental results. For 
this reason these limitations are discussed in detail in the section on 
environmental conditions. It is the authors' hope that this discussion 
will lead to the design of special equipment to overcome some of the 
limitations and so make possible a better understanding of the effect of 
the environment on plant growth and crop production. Such an understanding 
should eventually assist the plant breeders in developing more productive 
cultivars. 



Refrigeration systems 

It is advantageous for persons using the cold rooms and growth facilities 
to understand the basic principles involved in refrigeration systems. 
Figure 1 shows the main components in a simplified system which consists 
of a pump, condenser, receiver to store liquid refrigerant, expansion 
valve, and evaporator. 



r 



Condenser coil 
(cooled by water 
or air + fan) 



Receiver 
contains 
liquid 
refrigerant 



Expansion 
valve 



Pump 
compressor 



Cold room 



Evaporator 
coil 



Figure 1: Basic refrigeration system. 



- 9 - 



Provision for thermostatic temperature control of the space to be 
refrigerated is included in working systems. Such systems have a dryer 
to prevent any water vapor from freezing inside the system and plugging 
it with ice. Other protective devices and refinements are usually 
incorporated. 

The pump or compressor compresses the refrigerant gas. As it does so the 
gas warms up. The hot gas under high pressure is passed through the 
condenser where it is cooled and condensed into liquid. Cooling of the 
gas is achieved by circulating cold water or cold air around the outside 
of the condenser coils. The chilled refrigerant liquid under pressure is 
stored in the receiver until it passes through some type of control 
mechanism (commonly an expansion valve) which sprays it in the form of 
liquid droplets into the evaporator coil in which the compressor 
maintains a low pressure. 

The liquid refrigerant evaporates in the evaporator and the resulting gas 
expands owing to the low pressure. Both evaporation and expansion 
require that the refrigerants absorb heat and this results in a drop in 
temperature in the evaporator. The evaporator is situated in the space 
to be cooled or in an air duct supplying cold air to the space to be 
cooled. The compressor evacuates the cold refrigerant gas from the 
evaporator, compresses it, and passes it on to the condenser to repeat 
the cycle. The physical properties of the refrigerant gas place 
constraints on the temperature range over which it may be used for 
refrigeration: R 12 works easily down to -20°C but can be used to -30°C; 
R 22 works easily down to -30°C but can be used to -40°C; R 502 works 
easily down to -40°C but can be used to -50°C; R 292 (propane) + R 503 
(freon) work well from -50 to -130°C when used in a cascade refrigeration 
system. 

In practice, the temperature of the evaporator coil must not vary too 
much or else the air temperature in the cabinet cannot be held constant. 
In order to achieve this, some hot compressed gas is bypassed from the 
pump directly into the evaporator. The evaporator temperature is 
controlled by regulating the cycling of hot gas and cold refrigerant. 

In most working cold rooms the evaporator removes heat from the air in 
the cold room. The system is thermostatically controlled to keep the air 
in the cold room within a specified temperature range. When warm 
material is moved into the cold room, heat flows from the warm object to 
the room air to the evaporator. This means that the air temperature in 
the room rises. As long as the amount of material moved into the room is 
small or the temperature of the material is only a few degrees above room 
temperature, the rise in air temperature will be small. However, if a 
large amount of material at room temperature is transferred into a low 
temperature room, the air temperature in the cold room will rise several 
or even many degrees above the set temperature. The air in the room will 
remain above normal until most of the heat in the material has been 
transferred by convection to the evaporator. Rate of heat transfer will 
depend on the specific heat of the air (a fixed quantity) and the rate of 
air movement. If a large amount of warm material is moved at once into a 
cold room, the air temperature in the room will remain above normal for 



- 10 



several hours. Where accurate control of the room temperature is 
required, these effects must be avoided either by prechilling the 
materials to be placed in the room or by moving in small amounts of the 
material at suitably spaced intervals. 

Moving large amounts of cold material into a warm room will produce 
similar effects except that the room temperature will fall rather than 
rise. If very rapid chilling is required, the evaporator coil may be 
connected to a metallic plate. The material to be chilled is placed on 
the metallic plate which conducts heat from the material to the 
evaporator without the need for convection currents in air. Such a 
system is of no advantage if a whole room is to be chilled. 

Controlled temperature rooms are usually sealed to reduce leakage of warm 
or cold air into them from the environment and they are insulated to 
reduce heat transfer through the walls and doors. This makes possible 
much better temperature control within the room and reduces the power 
required to maintain the room temperature. Room doors should be kept 
closed as much as possible. 

Because the rooms are sealed dry ice (solid carbon dioxide) and liquid 
nitrogen should never be stored in an enclosed cold room. Both these 
materials will vaporize and the level of carbon dioxide or nitrogen in 
the room will rise. If the level of carbon dioxide rises above 10% it 
will cause persons exposed to it to become unconscious. In a cold room 
this can result in death either by poisoning or hypothermia. High levels 
of nitrogen result in asphyxiation and death. 

In order to chill a cold room or growth cabinet to a temperature below 
the freezing point, it is necessary to chill the outer surface of the 
evaporator coil to a temperature below 0°C. Under such conditions any 
water vapor in the cold room will be deposited as frost or ice on the 
evaporator and will build up to the point where it plugs the evaporator 
and stops air flow through it. Room temperature will then rise because 
convective cooling has been cut off. 

In practice, because water freezes at 0°C cold rooms cannot be maintained 
indefinitely much below 4°C with a single evaporator if really accurate 
temperature control is required. This problem is aggravated in a growth 
room or growth cabinet where energy must be added as light during at 
least part of the daily cycle. The best solution to this problem for 
research purposes is to use two evaporators. One is used to cool the 
room while the other is isolated from the room and warmed either 
electrically or by hot gas from the refrigeration system. This heating 
removes the frost and ice. This system is expensive and requires a 
system of mechanical dampers to isolate the evaporator being defrosted. 
It is, however, the only system that will provide accurate temperature 
control below 4°C in cold rooms. It is also the only system that can be 
used in growth cabinets if plants are to be grown under continuous light 
at low temperatures and if air temperatures are to be maintained 
accurately at temperatures below 5°C. In cold storage rooms where brief 
(up to 15-20 minutes) warm periods can be tolerated, a single evaporator 
may be used. When this evaporator coil is defrosted, air circulation is 



- 11 - 



cut off to the room. This system works well for cold temperatures near 
and just below the freezing point, but below -15°C it rapidly becomes 
unsuited to research needs as the temperature rises during defrost become 
progressively bigger and longer. With single coil systems the frequency 
and duration of defrosting is controlled by: 

(1) the amount of moisture to be introduced into the system with the 
material to be refrigerated, 

(2) leakage of water vapor into the room from a door opening or into 
the growth cabinet from the ambient air through cracks and seals 
around the doors (growth cabinets cannot be air-tight or carbon 
dioxide levels would fall too low for plant growth) , and, 

(3) the design of the evaporator coil and refrigeration system. 

Good design makes possible several days of sub-freezing operation for 
application of cold stresses to test the hardiness of cold hardened plant 
material. For such work, excellent room design is also needed to prevent 
the development of layering of the air (producing a temperature gradient) 
and cold spots within the room. Cold hardened plants are extremely good 
thermometers and will react to temperature differences of as little as a 
few tenths of a degree C. 



Temperature measurement 

Temperature control is an important feature of a controlled environment 
facility. Several devices are used for temperature measurement and these 
differ considerably in speed of response. A measuring device with slow 
response time may show a greatly reduced range of fluctuation in 
temperature in an environment with rapidly varying temperature. For 
example, the apparent magnitude of the high temperature spike occurring 
during defrost in a low temperature cold room lacking a dual evaporator 
will be greatly reduced while its duration will be increased as the speed 
of response of the temperature-measuring device decreases. 

Of the devices used for temperature measurement, liquid bulbs (e.g., 
glass-alcohol or glass-mercury thermometers and some of the older style 
chart recorders) and bimetallic strips have slow response times. Their 
use tends to conceal the poor temperature control of cold rooms operated 
below -15°C without dual evaporators. Well designed thermistors have 
much better response times but have a linear response to temperature only 
over narrow temperature ranges. This problem can be overcome by proper 
electrical circuitry. Resistance bulbs (resistance wire wrapped around 
ceramic) can be designed with moderate response times and are useful 
where it is desirable to average a rapidly fluctuating temperature. 
Thermocouples (especially ones made with very fine wire) have rapid 
response times. For best results, the actual thermocouple and a length 
of lead wire should be in the same temperature environment. This reduces 
the heat conduction between the environment of the leads and the actual 
junction. This precaution increases accuracy when the leads must pass 
through environments with widely differing temperatures. Thermocouples 
work conveniently with chart recorders, digital displays, dataloggers, 
and computers. 



- 12 - 



Light 

The description and measurement of light provided to plants present 
special problems. Light is radiant energy in a certain portion of the 
electromagnetic spectrum. For the present purposes it encompasses 
radiation with wavelengths from 290 mu to 850 mu, those wavelengths 
that affect plant growth. Different groups of wavelengths provide the 
energy for different processes within the plant. Some of these processes 
have been little studied. As a result, investigators cannot be sure of 
what should ideally be measured. 

The most important process in plants requiring light is photosynthesis, 
which is responsible for providing the energy required for plant growth. 
In higher plants, chlorophylls a and b are the pigments that absorb 
the light for photosynthesis. These pigments absorb in the blue and red 
portions of the spectrum. Among angiosperms, the synthesis of the 
chlorophylls and of the chloroplasts themselves is light-dependent. Both 
light intensity and quality appear to be involved in regulatory effects. 
The conversion of protochlorophyllide to chlorophyllide a is 
light-dependent in the angiosperms (absorption bands in blue and red). 

Phytochrome is another important plant pigment system. It is involved in 
the regulation of plant growth, especially in seed germination in some 
species, dormancy in woody plants, and in the photoperiodic control of 
flowering. The pigment exists in two interconvertible forms. One form 
absorbs in a band around 660 mu (P r ) and the other in a band around 
730 mu (Pp r ). Pp r is slowly converted into P r in the dark. It is the 
proportion of these two forms in the plant that determines the growth 
responses of the plant. The proportion and timing of application of 
these wavelengths in the diurnal cycle are therefore important in 
regulating plant growth. 

Plants also contain other pigments such as flavins and carotenoids that 
absorb light in the blue end of the spectrum. Phototropism is one system 
activated by such light. The pigments involved have not been identified 
with certainty. Other light-sensitive systems may exist and may be 
detected by comparing plant growth responses in the field with those in 
the greenhouse or growth cabinet. 

Light intensity and total energy received per day are also known to 
affect plant growth. Responses known as HER or high energy responses 
occur, but little is known about them except that high light levels are 
required for their initiation. 

Day length, the proportion of the normal 24 hour day in which light is 
supplied, is also very important in regulating rate of development of 
many species. The phytochrome system is involved in those responses. 

The multiplicity of light-sensing systems in plants greatly complicates 
the already difficult problem of measuring the light supplied to the 
plants. 



- 13 - 



Three units developed for different purposes are in common use for 
measurement of incident light energy. These are the lux (1 lux = 0.093 
foot-candles), the microeinstein per second per sguare meter (uE sec - ^- 
m~ 2 ), and the watt per square meter (W/m 2 ). 

The lux (1 lumen per square meter) and foot-candle (1 lumen per square 
foot) were units developed by lighting engineers to measure illumination 
for situations in which the ultimate light receptor is the human eye. 
The standard human eye is most sensitive to yellow light of 555 mu. 
Equipment for measuring illumination is readily available. However, some 
of it is not very accurate. 

Measurements of illumination have been criticized by plant scientists 
because the spectral responses of the human eye and plants are not 
similar. However, the same criticism applies to both the other units of 
measurement of incident light (uE sec -1 m~ 2 and W/m 2 ) since neither of 
these units evaluates the energy from different wavelengths in the same 
way as a plant does. The only inexpensive solution to this problem is to 
specify exactly the light source used and to include data on voltage and 
power. For fluorescent light, the phosphor should be specified (e.g., 
cool white, daylight, wide spectrum grolux, etc). If more than one 
source is used (e.g., cool white fluorescent and incandescent), separate 
data for each of the sources should be provided. 

The microeinstein sec"-*- m -2 is a unit developed to measure photon 
flux by scientists interested in photochemistry. Radiant energy 
(including light as defined above) is considered to be made up of 
discrete particles called quanta or photons. The energy of a photon 
depends on its frequency (inverse of wavelength) according to Planck's 
law (E = hv) where E = energy in ergs per sec, h = 6.62 X lO -2 ^ ergs 
per sec (Planck's constant) and v = frequency in cycles per sec. A 
consequence of this is that photons of different wavelengths or 
frequencies carry different amounts of energy. One molecule can absorb 
one photon at a time. Ideally, a condition seldom realized, if a gram 
molecule (mole) of photochemically reactive substance absorbs 6.022 X 
10" (the number of molecules in a mole) photons or quanta of light, it 
should become activated to produce a mole of product. An einstein is 
6.022 X 10 2 ^ (Avagadro's number) photons, a sufficient number of 
photons to activate 1 mole of photochemically reactive compound. 

The watt/m 2 is the unit used by physicists to measure irradiance or 
power per unit area. 

Many workers use the term PAR or photosynthetically active radiation. It 
measures the irradiation in the 400-700 mu waveband in W/m 2 or the 
photon flux density in the same waveband in uE sec"^- m -2 . This 
sort of measurement ignores the formative effects of different 
wavelengths on plant growth. 

The ideal solution to the problem of light measurement would be to 
provide a plot of wavelength against incident energy to cover the whole 
spectrum of interest for plant growth. This solution has serious 
disadvantages in that the necessary equipment is expensive and reporting 
of the results requires a table or graph. 



- 14 - 



Accurate interconversions among these units are complicated (see Appendix 
14) and require accurate information about the spectral distribution 
curve of the radiant energy from the source. Approximate conversions may 
be made using empirical factors tabulated by McCree (1981), but such 
conversions require a knowledge of the light source. 

In practice, the maintenance of a nearly constant light level in a growth 
cabinet requires constant monitoring. Light bulbs, both fluorescent and 
incandescent, burn out. Ballasts for fluorescent lights fail. The light 
output of fluorescent lights decreases with age. The drop is rapid 
during the first 100 hours of operation and the rate of drop gradually 
decreases subsequently. The ideal solution to these problems would be to 
mount a photocell inside the growth cabinet and connect it to a recorder 
or digital output. 

The light output of fluorescent lights is temperature-dependent. It 
drops off at high temperatures (above 35°C) and at low temperatures 
(below 10°C). Since it is the actual tube temperature that is critical, 
the limits for operation to provide adequate light output will depend on 
air circulation around the lights. 

For really critical work on light quality, the spectral distribution of 
the radiant energy should be checked periodically. There have been 
reports of changes in the spectral distribution of output from at least 
some of the more specialized fluorescent lights. 



Humidity 

Control of the amount of water vapor in the atmosphere of a growth 
cabinet is important because it influences the transpiration rate of the 
plants in the chamber. Transpiration rate is partly determined by the 
difference between the water vapor pressure inside the leaf and that in 
the ambient air, assuming that air circulation around the leaves is rapid 
enough to prevent the formation of a layer of air surrounding the leaves 
with a relatively high vapor pressure. The vapor pressure within the 
leaves will normally be close to that of water at the same temperature. 
The vapor pressure of water rises rapidly as the temperature rises. 

Relative humidity is the amount of water vapor in the air expressed as a 
percentage of the maximum amount of water vapor that the air could hold 
at the given temperature. Since the water vapor holding capacity of air 
rises with temperature, a rise in temperature of the air will cause a 
drop in relative humidity if the absolute amount of water vapor in the 
air remains constant. This explains why, in a growth cabinet with rapid 
temperature cycling (hunting), comparable rapid cycling of relative 
humidity occurs. The relative humidity will drop as the temperature 
rises and rise as the temperature drops. 

Four general methods are available for measuring relative humidity. 
First, there is determination of dew point. This type of method 
determines the temperature at which the air is saturated with water 
vapor. It is accurate but rather expensive. It may be used to monitor 



- 15 - 



conditions in a growth cabinet. Second, there are the wet and dry bulb 
thermometers, thermocouples, or thermistors. These measure the maximum 
temperature drop that can be caused by evaporative cooling in the 
atmosphere. Relative humidity is then determined from tables (Weast et 
al. 1985-86). This technigue can be used for measuring or monitoring the 
relative humidity in a growth cabinet. It is accurate and works well as 
long as the wick on the wet bulb sensor can be kept fully moistened with 
pure distilled water. The third group of methods depends on the change 
in physical properties (e.g., length of hairs, or electrical resistance 
of hygroscopic salts such as LiCl) of materials as the relative humidity 
of the surrounding air changes. This type of unit reguires careful 
calibration. Some units of this type are suitable for controlling and 
monitoring humidity in growth cabinets. The fourth method for measuring 
relative humidity is by infrared detectors. These are accurate but 
expensive. They depend on measuring the quantity of water vapor in the 
air by its ability to absorb infrared radiation of certain wavelengths. 

Four methods for humidity control are available at Lethbridge: 
refrigeration-reheat, chemical dryer, additive, and plastic bagging. 

With properly designed equipment, refrigeration-reheat is an accurate 
method for controlling humidity. It relies on removing excessive 
moisture from the air by chilling the air in the evaporator coils. The 
air temperature is then raised by introducing hot refrigerant gas into 
the evaporator. Temperature control is achieved by proper cycling of hot 
gas and cold refrigerant into the coil. The air to be chilled must be 
moist enough that water will condense on the evaporator coils when the 
air is chilled to the dew point. Proper evaporator design is also 
necessary to make sure that all the air leaving the evaporator is at the 
dew-point temperature. 

Chemical dryers are used where low relative humidities are required. 
These use a hygroscopic chemical to remove water vapor from the air. The 
chemical is usually regenerated by heating. 

Additive humidity control is useful only when relative humidity must be 
raised above the fairly dry conditions usually present in a growth 
cabinet. A humidity sensing unit controls addition of water by a misting 
or atomizing device or in the form of steam. Pure water (demineralized 
or distilled) or steam (not containing fungicides, bacterocides, and pH 
control chemicals often used to protect the condensate return lines) must 
be used. 

In plant disease research, relative humidity levels close to 100%, 
sometimes with dew present, are often required for infection studies. 
These levels can be obtained in growth cabinets by covering the plants 
with plastic bags, preferably in the dark. In the light, difficulties 
may be encountered with radiant heating. In a growth room this system 
can be scaled up and a plastic tent and humidifiers can be used to permit 
handling the large populations needed in plant breeding programs. It is 
especially useful where temperature control is required for good 
infection. 



- 16 - 

ENVIRONMENTAL CONDITIONS 

Cold rooms 

In controlled temperature rooms with minimum light (below 1 klx), it is 
usually assumed that all points within the room are at the same 
temperature. For critical work, this assumption should be tested by 
simultaneous temperature measurements using thermocouples and a recorder 
or datalogger of some type. The actual pattern of air movement within 
the room will determine how closely this assumption is realized. Very 
serious discrepancies (several degrees C) may occur in badly designed 
rooms. Placement of large amounts of material within the room may also 
affect patterns of air flow and temperature uniformity. 

Operation of a controlled temperature room at the freezing point poses 
special problems for biological research if the material must not freeze. 
Experience at Lethbridge shows that moist soil or vermiculite exposed to 
room air will freeze at air temperatures slightly above the freezing 
point even though stoppered flasks of distilled water in the same room do 
not freeze or supercool. This problem arises because the air movement in 
the room, which is essential for temperature uniformity, causes 
evaporation from the moist surface of the soil or vermiculite. Water 
must absorb heat in order to evaporate. Thus, heat flows from the soil 
or vermiculite to the water to facilitate its conversion from the liquid 
to the gaseous state and, in the process, the soil or vermiculite is 
chilled below the freezing point and the water in the medium freezes. 
The chilling is maintained after the soil freezes because water vapor 
continues to be formed by ice sublimation. Our solution to this problem 
is to raise the air temperature in the room. For our rooms, a temperature 
of 0.7 or 0.8°C is required to prevent exposed moist soil or vermiculite 
from freezing. An alternate solution to the problem would be to cover 
the surface to prevent the evaporative cooling. 



Plant growth cabinets and rooms 

INTRODUCTION The purpose of growth cabinets and growth rooms is to 
provide controlled, reproducible conditions for plant growth. At first 
glance it would appear that all that is required is to set the air 
temperature, intensity and duration of lighting, and relative humidity. 
For many experiments, reasonably reproducible results may be obtained by 
doing this, provided that the plants are to be grown at 20 to 25°C and 
that high light intensities and close humidity control are not required. 
If plants are to be grown under conditions such that a small change in 
conditions causes a measureable change in plant growth, then reproducible 
results are difficult to achieve in growth cabinets. However, overall 
trends can easily be detected but not quantified accurately. 

We have not studied these problems extensively at Lethbridge but have 
made some measurements that illustrate the magnitude and nature of the 
problems that will be encountered. Part of the data comes from work on 
cold hardening of wheat. 



- 17 - 



Under cold hardening conditions, rate of growth and length of leaves are 
very sensitive to small differences in mean temperature. Furthermore, it 
is probably true (Peacock 1975) that the apical meristem is the site of 
temperature reception, at least for control of leaf length. The meristem 
of young wheat plants is located below the surface of the growth medium. 
Although we have not performed replicated or even repeated experiments on 
the true microclimates, our experiences indicate the need for extensive 
serious research into the problems to be encountered. 

Temperature, light, humidity, air movement, watering, containers, 
nutrition, carbon dioxide, other gases, media and nutrients, diseases and 
pests will be discussed to the extent of our experiences. Temperature 
and humidity are probably the most difficult to control. Good humidity 
control reguires good temperature control. The temperatures experienced 
by the aerial parts of the plant depend on several factors: air 
temperature, air velocity, humidity, water status of plants, and light. 
The temperature of the below-ground parts of the plant will depend on air 
temperature, air velocity, watering, water content of growth medium, 
light, and container configuration. 



TEMPERATURE Measuring temperature in a cabinet where high levels of 
light are supplied for part or all of the daily cycle presents special 
difficulties because air movement is required to maintain temperature. 

It is conventional to measure air temperature at a site which is 
protected from the lights. In Conviron growth cabinets this is achieved 
by removing a small stream of air from a central location in the cabinet 
and passing it over the sensing unit, which is located in the machinery 
compartment. If an exposed thermometer is mounted in a growth cabinet in 
the light cycle, it will be observed that the temperature is higher 
closer to the lights. This response is caused partly by radiant heating 
of the thermometer and partly by air temperature. Plant leaves will 
experience this effect and its magnitude will depend mostly on the 
quality and intensity of the light supplied. 

Although the aerial parts of plants are surrounded by air, they are not 
necessarily at the same temperature as the ambient air. These 
relationships and the measurement of leaf temperature are discussed by 
both Salisbury and Tanner (see Tibbitts and Kozlowski 1979). Although we 
have done no work in this area, a summary of the situation is useful. 

Even if the air temperature is kept constant during the light and dark 
periods, there is no reason to expect that the plants will experience a 
constant temperature throughout the day. Plants will probably respond to 
the temperatures of their parts rather than to the ambient air 
temperature even though the latter will have a large effect on plant 
temperatures. In the light period the leaves will absorb a considerable 
amount of the energy radiated by the lights. This energy will be 
converted to heat which will raise the temperature of the leaves. Since 
the light intensity is not the same in all parts of a growth cabinet, 
these heating effects will be uneven. 



18 - 



Many but not all plants open their stomata during the light period. 
This serves two purposes. It allows uptake of carbon dioxide for photo- 
synthesis and sugar manufacture and for evaporation of water for cooling. 
This evaporation powers the transpiration stream for transfer of mineral 
nutrients from the growth medium to the leaves. Since evaporation of 
water reguires that the water molecules take up heat, evaporation will 
cool the leaves. This cooling will be influenced by a number of factors, 
some of which vary among plant species. These factors include: 

(1) internal leaf structure and abundance of stomata, 

(2) whether stomata are open or closed (controlled chiefly by light 
and water status of the plant), 

(3) water vapor pressure gradient between air in the interior of a 
leaf (usually close to saturation) and exterior air. This 
gradient will be influenced by relative humidity of ambient air 
and air movement over the leaf surface, 

(4) temperature (higher temperature means higher transpiration), 
which changes water vapor pressure gradient and affects stomatal 
movement, and 

(5) water status of plants, which is affected by availability of 
soil water. 

Orientation of leaves will affect the amount of radiant energy and 
consequently the leaf temperature. As the plants grow, additional leaves 
will be produced and these will usually shade the lower leaves thereby 
reducing the light energy that they receive and consequently their 
temperature. 

During the dark periods it is to be expected that leaf temperatures and 
air temperatures will be similar except in those species (e.g., succulents) 
with stomata open at night and those with a cuticle so thin that appreciable 
water loss occurs through the cuticle. Where appreciable water loss 
occurs from leaves in the dark periods, leaf temperatures will be below 
air temperatures because of evaporative cooling. 

Some factors that influence the temperature of the growth medium are 
container geometry, radiant heating, evaporative cooling, moisture 
content of growth medium, watering, cycling of air temperature, and size 
of plants. 

One of our first experiences with these problems involved container 
geometry. Wheat was being germinated and cold hardened at a constant 2°C 
under a 16 hour day of approximately 16 klx, provided by cool white 
fluorescent tubes plus a small incandescent supplement, in a vermiculite 
medium watered three times a week. Some of the plants were growing from 
seeds sown approximately 1 cm deep in wooden flats 25 x 39 x 9 cm filled 
to a depth of 7 cm with vermiculite. The others were growing in the same 
medium with the same watering schedule in green plastic pots (top 
diameter 15 cm, bottom diameter 10.3 cm, height 14 cm) beside the flats 
in the same growth cabinet. Plants in the plastic pots took 2 weeks 
longer to emerge. Crown temperatures in the plastic pots were not 
checked but were probably colder. 



- 19 - 



Moist soil surfaces may be chilled by evaporative cooling in the dark 
period or, if heavily shaded, by the plant canopy. During the light 
period, exposed soil surfaces are warmed by radiant heating. 

If the plants are watered with nutrient or distilled water that is much 
warmer or colder than the temperature of the growth medium, then the 
temperature of the medium will rise or fall respectively. This 
disturbance will persist for several hours (Fig. 2). Properly chilled 
water or nutrient for watering cannot be produced by storing it in the 
growth cabinet in which the water or nutrient is to be used as long as 
there is a light period in the cabinet. Under such circumstances, 
radiant heating will warm the nutrient. 

In a growth cabinet with an air temperature of 7°C and continuous light 
of 21.5 klx supplied from cool white fluorescent plus incandescent light, 
several temperature measurements were made. The temperature of nutrient 
in an unshaded carboy was 15.5°C. The temperature (mercury thermometer 
calibrated at 0°C with ice-distilled water) under an empty (no plants) 
flat of vermiculite was 7.3°C, on top of the flat it ranged from 10.5 to 
14.5°C (exposed), and a thermocouple at about 1 cm depth showed 16°C. A 
comparable flat containing a heavy canopy of 9-week-old wheat plants 
grown at 7°C with continuous light gave a temperature of 9°C at plant 
crown level (Fig. 2). This provides a dramatic example of the effect of 
shading the surface of the medium on the temperature of the medium under 
lights. 

Similar shading responses and appreciable variability were observed in 
experiments similar to the above except that the air temperature was 
maintained at a constant 3°C (under 21.5 klx of continuous light). A 
flat with 4- to 5-week-old seedlings showed crown temperatures of 7°C. 
Differences in crown temperatures of 2 to 3°C have been observed in 
plants grown in flats under apparently similar conditions. Differences 
in plant growth have been noted under these conditions. 



- 20 




Time, hours 



Figure 2. Effect of watering with nutrient at 20°C on crown temperature 
of 9-week-old plants grown in medium grade vermiculite in flats 25 x 35 x 
9 cm filled with 7 cm of vermiculite. Plants were grown at a constant 
temperature at 7°C under 21.5 klx of cool white plus incandescent light 
continuously . 



For a proper study of leaf length (a trait correlated with cold 
hardiness) of wheat grown under cold hardening conditions, these 
temperature aberrations will have to be controlled. One requirement will 
have to be that nutrient or water used for watering is prechilled in a 
dark cold room run at the proper temperature. 



Figure 3A shows data on crown temperatures of wheat plants being cold 
hardened under a regime frequently used at Lethbridge. This regime 
provides 8 hours of darkness at an air temperature of 4°C and 16 hours of 
9.7 klx of cool white fluorescent plus incandescent light with an air 
temperature of 6°C. Minimum dark-period crown temperatures approximated 
minimum air temperatures but maximum light-period crown temperatures were 
4°C higher than maximum air temperatures. The evaporative cooling effect 
in the dark was not detected and was probably relatively small in this 
test, but radiant heating effect was quite large (4°C). 



- 21 - 




Light 




9 



12 



15 



18 



21 



- 1 
24 



o 

o 



i_ 
3 
+•» 

CO 

k_ 



a 

E 

c 

O 

\- 

o 

c 

i5 
Q. 



20 - 



16 - 



12 - 



8 - 



4 - 




2 4 

Time, hours 



Figure 3. Plant crown temperatures during a complete temperature and 

light cycle; _ _ _ _, programmed temperature; , temperature of 

crown depth; t p m , temperature of crown depth in flat with no 

plants. 

A. Flats with plants growing under 24-h period with 8:16 h and 4:6°C 
light:dark, and 8-10 klx cool white fluorescent plus incandescent light, 

B. Flats under 6-h period with 4:2 h and 2:20°C, and 27 klx cool white 
fluorescent plus incandescent light. 



- 22 - 



In studies on days to head of wheat grown at a constant 20°C under 16 
hours of 21.5 klx of cool white fluorescent plus incandescent light, 
growth response problems have not been observed although similar types of 
temperature discrepancies occur. For example, in pots (1 gallon black 
plastic, diameter 15 cm, height 17.5 cm filled with soil) exposed to 20°C 
with no plants, the day temperature at 2.5 cm depth in soil was 23 °C and 
the night temperature was 20°C. The changes in temperature under these 
conditions occurred over about a 2-hour period. In comparable pots with 
a good plant growth, the day and night temperatures were 21 and 20°C 
respectively. An exposed (i.e., not shielded) thermocouple in the plant 
canopy recorded 23°C in the light cycle and 20°C in the dark. The change 
from light to dark values occurred in a few minutes. If the pot was 
watered with tempered water (water at the temperature of the cabinet) in 
such a way that all water was applied directly to the soil surface, the 
temperature in the plant canopy changed little (ca. 1°C) . If, however, 
the tempered water was sprinkled over the plant canopy, the temperature 
(exposed thermocouple) in the plant canopy fell from 23 to 20°C. The 
drop occurred over about 1.5 hours and had not recovered to 22°C until 
about 2 to 2.5 hours later. This behavior is the result of evaporative 
cooling induced by moisture on the thermocouple or the nearby leaves. 
Although we realize that exposed thermocouples should not be used to 
measure temperatures in high levels of light, nevertheless the plant 
leaves are exposed and radiant heating is one of the factors affecting 
leaf temperature. Further, we should realize that a plant leaf will 
respond to the leaf temperature rather than to the air temperature. 

For a plant such as wheat, which possesses an underground growing point 
for several (spring types) to many (unvernalized winter types) weeks, the 
interpretation of experiments using large daily temperature changes is 
difficult. Figure 3B provides actual temperature data from crown depth 
in a flat of vermiculite with no plants and a flat with plants from an 
experiment in which a 6-hour temperature and light cycle was used. Under 
these circumstances, the daily temperature range is smaller under a plant 
canopy than in a flat without plants and the maximum and minimum 
temperatures are 6 and 8°C lower and approximately 4°C higher than the 
maximum and minimum air temperatures, respectively. Discrepancies 
between maximum and minimum air and crown-level temperatures were less 
when the length of the cycle was increased to provide 16 hours at 20°C 
(light) and 8 hours at 2°C (dark). The rate of rise and fall of the 
temperature at crown level after a change in air temperature was found to 
be greater in a relatively dry flat (2 days after watering in a flat with 
good plant growth) than in a relatively wet flat (shortly after watering 
in a flat with good plant growth) . This effect was not noticed within 2 
days in a flat of vermiculite with no plant growth. 

It is assumed that water loss from a flat with good plant growth is much 
greater than that from a flat with no plant growth. Thus, the plant 
population in a container controls water levels in the medium and 
consequently the exact pattern of daily cycling of crown level 
temperatures. 



- 23 - 



LIGHT The irradiance over the growth area of a growth cabinet is not as 
uniform as the air temperature. In the corners it may be only 80% of 
that near the center. The conseguences of this may not be serious at 
lower light intensities or normal (ca. 20°C) air temperatures. However, 
at higher light intensities and low (1 to 10°C) air temperatures, the 
lower light levels will result in lower effective temperatures (i.e., 
temperatures experienced by the plant) . Differences in growth rate and 
morphology may be apparent. 

Increases in the day length may cause changes in growth rates of plants 
which are doubtless the result of changes in the effective temperatures. 
For example, wheat sown and grown at 2°C under continuous 16.1 klx of 
cool white plus incandescent light emerged in 11 to 12 days, whereas when 
the air temperature was 3°C and only 16 hours per day of comparable light 
was provided, emergence took 4 to 5 weeks. With an 8-hour day at 3 . 2 klx 
at 3°C, emergence occurred after 6 weeks. 



HUMIDITY For most of the research in growth cabinets at Lethbridge we 
have not found humidity control to be necessary. When higher humidities 
have been needed, they have been obtained by keeping water in the tray in 
the floor of the cabinet. 

However, for studies on water relations humidity control is essential. 
If work on water content and cold hardiness is to be undertaken, special 
difficulties will be encountered since dew points below freezing will 
probably be needed. 



AIR MOVEMENT Air movement has been reported to be a determinant of plant 
growth but it has been little studied under controlled conditions. 

Air movement will influence leaf temperature by increasing transpiration 
and conseguently evaporative cooling. Air movement will also increase 
the availability of carbon dioxide by preventing air stagnation around 
the leaves. 

Except for their effect on temperature, responses to small changes in air 
movement seem to be quite small. However, under cold hardening 
conditions (2 to 3°C with light), growth differences on two sides of a 
growth cabinet with upward air flow have been observed. These have been 
traced to differences in air flow on the two sides of the cabinet caused 
by small differences in fan speeds between the two fans serving the sides 
of the cabinet. Such problems have not been encountered with plants 
growing at 20 to 25°C. 



WATERING An adequate water supply is essential for plant growth. 
Controlling the supply of water presents serious difficulties and the 
available methods are limited because of the peculiarities of water 
movement within soils and other plant support media. 



- 24 - 



The most satisfactory method of supplying water is to use a solution 
culture (hydroponics). This technique requires that the roots be 
immersed in a very dilute solution of mineral salts (see Fig. 4). For 
many but not all plant species, the solution must be aerated by bubbling 
air through it to supply sufficient oxygen for healthy root development. 
The water lost by transpiration has to be replaced, as do the mineral 
salts taken up by the plant. This can be done manually by changing the 
nutrient solution at frequent intervals (frequency increasing as the 
plants grow) or by an automated system that replaces both water and salts 
taken up by the plants. Automated systems require frequent monitoring to 
ensure that no malfunctions have occurred. 

Sand or gravel culture methods are also satisfactory if the system is 
carefully designed and operated. Watering with nutrient solution can be 
done from above or below. Watering from above is usually more 
satisfactory in growth cabinets. It is accomplished by allowing nutrient 
to drip on to the upper surface of the medium from tubing (plastic 
preferred) with regularly spaced small holes. Large-bore tubing, careful 
levelling of the system, and careful checking of hydrostatic pressures 
and flow rates are needed to ensure uniform watering. Flow rates must be 
great enough to prevent excessive salt accumulation in the medium as this 
will injure the plants. Facilities for drainage are necessary. Watering 
from below is achieved by periodically pumping nutrient up through an 
opening into the bottom of the container and allowing it to drain out. 
An overflow must be provided to control the maximum depth of nutrient in 
the container in each cycle. Large-bore tubing must be used and the 
system carefully checked to ensure that rate of nutrient flow into and 
drainage out of each container are similar. If this is not done, 
watering and growth will not be uniform from one container to another. 
Both systems of sand or gravel culture may be partially or completely 
automated. They should be monitored frequently and regularly to check 
for proper operation. For work between and 15°C and at high 
temperatures above 30°C, tempered nutrient should be used to avoid the 
root and crown temperature effects described elsewhere. 

Where levels of precision are satisfactory, manual watering with nutrient 
from a hose or watering can may be used. 

If careful control of plant nutrition is not necessary, plants may be 
grown in fertile soil and watered with tap water from a hose. Tempered 
tap water is preferable, especially in areas where the tap water may be 
cold (below 10°C) for part of the year. 

Studies on the responses of plants to prolonged water shortages when 
grown in soil present special problems which arise from the behavior of 
the soil water system. 



- 25 - 



Cross section 



vermiculite 



fine mesh 
plastic screen 




waxed wood 



removable waxed 
wood 



1 quart plastic container with 
sides painted green ( to 
prevent algae growth in 
medium) 



Top View 



removable waxed wood 




Figure 4. Containers used for solution culture of cereals at Lethbridge, 



- 26 - 



Two rather imprecise terms, field capacity and permanent wilting point, 
are often used by plant physiologists to describe the water status of a 
soil. At field capacity (water potential usually above 30 kPa) the soil 
contains the maximum water content possible without drainage of water 
occurring from it under the force of gravity. At the permanent wilting 
point (usually -1000 to -2000 kPa) plants will wilt and remain wilted 
even when transpiration ceases. Both these "constants" are affected by 
soil type and the latter is affected, in part, by the test species of 
plant that is used. 

In addition to water vapor, water in the soil exists in the following 
intergrading categories: 

(1) adsorbed on soil particles; this form requires large forces to 
move it, 

(2) held by surface tension in the capillary pores in the soil, 

(3) free water in the large pores. The latter is the only category 
that moves under the influence of gravity alone. When all large 
pores are full of water, the oxygen supply to the roots is very 
poor and only plants adapted to such conditions will grow 
properly. 

Except in soils completely saturated with water, water movement in soil 
is chiefly along a water potential gradient (i.e., gravitational forces 
are unimportant) . In the field, the chief force drawing water down to 
lower levels is derived from the low water potential of the drier soils 
at those levels. In the bottom of a well watered pot with drainage 
holes, such lower levels of dry soil do not exist, so the water potential 
at the drainage holes is near kPa and water tends to accumulate in the 
bottom of a pot and slowly drain out under the influence of gravity. 
This results in a waterlogged layer in the bottom of a well watered pot 
or flat. 

When dry soil is moistened with water, the water is adsorbed on the soil 
particles and the capillary pores fill with water before there is any 
free water that can move readily in the soil. This means that when soil 
is watered the water content must rise to field capacity before much 
water movement occurs. So, in a pot being watered there is a sharply 
defined front between the dry and wet soil (at field capacity). It is 
therefore not possible to water a pot full of uniformly packed soil and 
end up with a pot full of uniformly wet soil with a water content below 
that of field capacity. When a pot of uniformly dry soil is watered, the 
end result is either a pot full of soil at field capacity or a pot with 
an upper layer of soil at field capacity and a lower layer of dry soil. 
If the soil in the pot is caked or crusted, free water may flow to lower 
soil layers down cracks or down the inside of the sides of the pot. 

The usual way of controlling water in plants grown in soil for studies of 
drought tolerance is to water the pots to field capacity, weigh the pots, 
and add water as soon as the water content falls to a certain predetermined 
level. This produces an environment with a fluctuating water supply to 
the plant. 






- 27 - 



In a pot with growing plants the situation is somewhat different. Roots, 
which are usually not uniformly distributed, can lower the water 
potential in the soil to the permanent wilting point. Thus, roots tend 
to produce a region of dryish soil (between the permanent wilting point 
and field capacity) around them. Adequate watering raises the moisture 
content back up to field capacity. 



CONTAINERS Container size, shape, and color should be standardized. 
Container size can influence the required frequency of fertilization if 
soil is used as a growth medium. As the nutrient supply in small 
containers will be depleted sooner than in large containers, symptoms of 
mineral deficiencies will appear sooner in small containers. The color 
of the containers may affect soil temperatures as a result of the 
container's ability to absorb light energy during the light cycle. Clay 
pots can produce two side effects. The clay walls adsorb nutrients and 
later release them by processes similar to those exhibited by soil 
particles. The walls of clay pots are porous so that moisture from the 
soil diffuses through them and evaporates from the surface. This will 
cool the pot and its contents. Container geometry can affect the 
temperature of the medium as discussed in the section under temperature. 



NUTRITION AND MEDIA Ten elements (macronutrients) are required in 
moderate to large amounts for plant growth. Water supplies hydrogen and 
oxygen. Carbon dioxide in the air supplies the carbon. The 
others--calcium, magnesium, nitrogen, phosphorus, potassium, sulfur, and 
iron — are supplied by the soil. In addition, six elements (boron, 
chlorine, copper, manganese, molybdenum, and zinc) are required in trace 
quantities (micronutrients) . Halophytes require sodium. Cobalt is 
required for the symbiotic fixation of nitrogen by legumes. Excessive 
quantities of the micronutrients and most macronutrients can be toxic. 
If nutrients are supplied to sand or gravel culture containers from 
above, either from watering cans or by drip irrigation, care must be 
taken to supply sufficient nutrient to flush excess salts from the medium 
or salts will build up and may become toxic. 

The nutrient solution most often used at Lethbridge is a modification of 
Hoagland's No. 1 (see Appendix 13) with the iron supplied as iron 
citrate. Because use of ferrous sulphate resulted in iron deficiency 
symptoms in wheat, iron citrate recommended by Hewitt (1952) was used 
instead. It is satisfactory but troublesome to dissolve. 

Three growth media are used at Lethbridge. These are soil, Cornell mix 
(see Appendix 12), and vermiculite. The history of the soil in use at 
Lethbridge Research Station has been known since 1906. It was obtained 
from the headland of one of the Research Station experimental areas when 
a road was widened. No pesticides or fertilizers had been used on the 
land and it had been sown to grass for many years. The soil was collected 
several years ago and is expected to last another 15 to 20 years. 



- 28 



When it was available, a fine (No. 5 or plaster aggregate) grade of 
vermiculite was the most satisfactory. No. 3 or medium grade vermiculite 
is now being used. Seed is sown directly into dry vermiculite. As a 
precaution, we find it necessary to wash the vermiculite thoroughly with 
distilled water when the seed is moistened. This serves to flush out 
some unidentified water-soluble toxin that has been found occasionally in 
the vermiculite we use. The toxin prevents seed germination and results 
in wheat plants with short dark green leaves. 



CARBON DIOXIDE Carbon dioxide is the substrate for photosynthesis and by 
far the most important carbon source for green plants. It is freguently 
the limiting factor that controls the rate of photosynthesis. Two other 
potentially limiting factors are light and temperature. When carbon 
dioxide levels fall to low limiting values they control the rate of 
photosynthesis, and increases in light and or temperature will have 
little or no effect on the rate of photosynthesis. Because of their 
effect on the rate of photosynthesis, changes in CO2 levels will affect 
growth rate. There are reports in the literature suggesting that CO2 
may have additional biochemical and morphological effects on plant growth 
(Strain 1978). 

Carbon dioxide levels in the atmosphere have been gradually rising. It 
is believed they were around 275 ppm before the industrial revolution. 
By 1900 they had risen to approximately 290 ppm, by 1960 to 320 ppm, and 
by 1976 to close to 330 ppm. They are thought to be increasing at around 
0.7 ppm per year at present. They tend to rise in winter and fall in 
summer due to photosynthetic uptake by plants. The annual range is 
around 6 ppm. 

Human activity affects local CO2 levels. Levels are high in large 
cities with lots of human activity and oxidation of fossil fuels and low 
in the rural areas, especially in summer. In houses and office buildings 
they rise to 600 ppm. Levels of carbon dioxide above 2% may cause toxic 
symptoms in plants if they persist for long periods of time. 

In a sealed growth cabinet, CO2 levels will fall rapidly during the 
light cycle. C-4 plants like corn can lower CO2 levels in the light 
cycle to 50 ppm and C-3 plants like cotton can produce C0 2 levels up to 
150 ppm. The presence of an investigator in a walk-in growth room may 
raise the CO2 levels to between 500 and 600 ppm. During the dark 
cycle, CO2 levels will rise due to plant respiration. 

Prevention of large changes in C0 2 concentration will require 
impractically great rates of air exchange between outdoor air and growth 
chamber air. Such exchanges are theoretically calculated to be as high 
as 75% of chamber volume per minute. Exchange with ambient air may cause 
problems if there is much human activity in the room surrounding the 
plant growth room (high C0 2 ) or if there are many plant growth chambers 
in the vicinity (low C0 2 if all lights are on at the same time). 



- 29 - 



Commercial plant growth cabinets have provision for exchange of outside 
air. Such provision, however, falls short of that required to maintain 
CO2 levels in a cabinet full of large, rapidly growing plants. To some 
extent this is compensated for by the fact that most commercial cabinets 
are not very air-tight, a fact attested to by the problems of maintaining 
low humidities inside them. 

Controlled additions of CO2 (free from compressor oils) to the growth 
cabinet atmosphere are the best way to control C0 2 levels in the light 
cycle. Removal of excess CO2 during the dark cycle poses greater 
problems and there is not universal agreement on a satisfactory method 
for achieving this. 

Control of CO2 levels requires monitoring. The most accurate method of 
determining CO2 is with an infra red gas analyzer. This equipment is 
expensive and requires careful operation if accurate data are to be 
obtained. A cheaper system is based on the fact that, as CO2 
concentration in distilled water increases, so does electrical 
conductivity. The air to be analyzed is bubbled through water which is 
then passed through a conductivity cell. Both of these methods may be 
connected to an automated system for additive control of CO2 levels. 



OTHER GASES The control of oxygen levels is not normally required in 
growth cabinets studies, even though modified levels are used 
commercially for fruit storage and ripening. 

Sealed growth cabinets may be used for study of air pollutants. With 
such units it must be remembered that plants, especially those with 
ripening fruits, give off ethylene, a plant growth regulator causing 
epinasty and accelerating leaf fall and fruit ripening. With very 
sensitive plants it may be necessary to filter the ventilating air to 
remove air pollutants. The topic of pollutants is not under investigation 
at Lethbridge and its detailed discussion is outside the scope of this 
bulletin. 



DISEASES AND PESTS The discussion of diseases and pests will be confined 
to those diseases and pests which are or have been a problem in the 
Phytotron and greenhouse at Lethbridge. The problems are to some extent 
determined by the crops that are grown and by the diseases and pests 
prevalent in the outdoors. 

The most important aspect of disease and pest control is prevention. 
In practice, this means sanitation. Sanitation is the biggest problem 
in greenhouses. 

Normal growth cabinet operation usually involves completely removing one 
crop before the next one is planted. If the cabinet is left empty for a 
week or two, or if a very high temperature is maintained for a shorter 
period of time, the pests will be eliminated. Leaving the cabinet empty 
allows time for preventive maintenance of the refrigeration equipment and 
permits thorough cleaning. The first step in cleaning is to remove all 



- 30 - 



plants and plant debris, followed by sweeping and vacuuming. Then the 
growth cabinet floors are removed and soaked overnight in "Lime-a-way" (a 
commercial descaling preparation with phosphoric acid as the active 
ingredient), and later rinsed with water. The tray under the floor is 
vacuumed and rinsed. If the tray is heavily crusted with salts, 
Lime-a-way is used to remove all scale and dirt. Finally, if necessary, 
the cabinet walls are washed with soap or detergent. 

Care is taken to avoid introducing diseased or insect-infested plants 
into the clean cabinets. Since we have a large operation, greenhouse 
staff on weekdays can be assigned to look after specific areas. This 
reduces the chances of a pest or disease moving from one area to another 
(e.g., from greenhouses to growth cabinets) on staff clothing or bodies. 
Cabinet doors are kept closed as much as possible since many of the 
problems enter through the doors and spread out from the areas around the 
doors. 

Greenhouse sanitation is a much greater problem largely because there is 
such a temptation not to clean out all the plants from a greenhouse 
compartment or room at one time. Even a few plants under the benches can 
harbor small residual populations of the more troublesome pests. For 
best results, expanded metal rather than wooden bench tops are used. 
Gravel floors have been replaced with concrete. Both these changes have 
reduced our pest problems. Between experiments, all plants and plant 
debris are removed from a greenhouse compartment or room. The floors, 
including all corners and areas under the benches, and the metal tops are 
flamed with a propane weed burner if there has been a pest or disease 
problem and usually a very high temperature is maintained for two or 
three days to eliminate the pests. 

Most greenhouse pests come in from outdoors. The entry of some of these 
can be prevented by screening the openings. Air introduced in the summer 
through the swamp coolers is filtered of pests that might enter with the 
incoming air. The positive pressure built up in the greenhouse also 
helps prevent the entry of diseases and pests. 

Powdery mildew (Erysiphe sp.) is a problem on cereals and some other 
crops in the greenhouse and growth cabinets. It produces small, white, 
powdery lesions on the leaves and stems. It tends to be more serious 
under conditions of low light in the winter in the greenhouses. Spread 
is rapid. Problems in growth cabinets develop on older plants, probably 
because the growth cabinets are cleaned before seeding and it takes time 
before the disease is introduced into the cabinet. It is uncommon on 
cereals under hardening conditions, probably because of the low 
temperature. Spraying with Bayleton is the best method of control in a 
growth cabinet. Fine sulfur dusted over the plants works well in a 
greenhouse, but sulfur is too corrosive for regular use in a growth 
cabinet. 

Damping off (caused by one or more of several fungi including Pythium, 
Rhizoctonia, Fusarium, and Phytophthora spp.) is sometimes a problem, 
especially when seeds are planted deep. It does occur in the 
greenhouse. Where Pythium is the chief problem, proper watering is 



- 31 - 



important. Plants must not be allowed to dry out too much nor should 
they be overwatered. Captan or other seed dressings can be used as a 
fungicide for partial control. Soil sterilization is sometimes 
recommended but a sterile soil is an excellent medium for growth of fungi 
that cause root diseases because sterilization removes competing 
organisms . 

Rusts have not been a problem because the climate of the Lethbridge area 
is too dry for a rapid buildup in most years. 

Healthy seed is used to reduce seed-borne diseases. 

In general, the use of persistent systemic insecticides and miticides is 
avoided for control of pests. Some of these systemics are quite toxic to 
humans, a property shared with many other insecticides and miticides. In 
an institution like ours, where entomological research is carried out, 
care must be taken, especially with persistent systemics, to avoid 
contamination of the phytotron and greenhouses since some scientists use 
these facilities for studying insects. 

The greenhouse staff have been trained in using pesticides. They wear 
proper protective clothing when applying pesticides. Treated areas are 
sealed off as far as possible and posted with necessary warning signs. 

The two-spotted spider mite, Tetranychus urticae, is a serious 
problem. Mites usually feed on the underside of leaves by sucking the 
plant juices. They produce small, pale-colored spots lacking the tiny 
black spots characteristic of thrip damage on leaves. They may be seen 
and identified with a magnifying glass since they have eight legs, 
whereas adult insects have only six legs. In a growth cabinet, they are 
controlled by spraying with Pentac, Kelthane E, Morestan, and Vendex 50 W. 
In the greenhouse, fumigation with Plantfume 103, DDVP, or Tedion is 
satisfactory. These compounds are too toxic to humans for use in a 
growth cabinet or growth room. 

Various species of aphids are a problem because they suck plant juices, 
may transmit virus diseases, or inject toxins into plants. Aphids have 
six legs and are usually present in a wingless form. However, most 
species have at least one winged form in their life cycle. Fumigation 
with nicotine is effective in the greenhouse. In a growth cabinet or 
growth room, one or two sprayings with Pirimor is sufficient for control 
in a cereal, canola (rape), or saf flower crop. 

Thrips are tiny insects that suck plant juices. Their presence is 
indicated by small pale spots on the leaves. The spots are associated 
with tiny black dots (feces) which help differentiate thrip infestations 
from mite infestations. Fumigation with nicotine or Plant Fume 103 gives 
good control in the greenhouse. Spraying with orthene works in the 
growth rooms and growth cabinets. 



- 32 - 



Whitefly, Tcialeurodes vaporariorum, used to be a problem in the 
greenhouse, especially on beans. They have not been a problem in growth 
chambers and growth rooms. With the introduction of all the sanitation 
methods described above, whiteflies have been largely eliminated from the 
greenhouses. They may be controlled by spraying with Ambush. 

Mealybugs also were a problem. They are flattened oval insects, usually 
without wings, 3 to 7 mm long and covered with a white powdery wax. They 
have been eliminated from our greenhouses by sanitation procedures. 

Fungus gnats or manure flies (Platyura sp. and Sciara sp.) occur 
occasionally and are controlled by malathion drenches. 

Algae can cause problems. They will grow in the nutrient solutions used 
for watering. Such solutions must be kept in the dark or covered with 
green garbage bags to exclude the light. Although they grow on the 
surface of media at cold hardening temperatures (i.e., to 10°C), they 
have not caused problems. Sanitation of cabinets prevents serious 
buildups. 

Mice are a recurring problem, mostly in the greenhouses. We also have 
had them in the controlled temperature rooms at 25°C when seed was being 
stored for conditioning in the room. They often appear in the fall in 
the greenhouses. They dig up and eat newly planted sprouting seeds, eat 
ripe and ripening seeds on the plants, and chew off the heads of wheat. 
All seed should be stored in mouseproof containers. Mice are best 
eliminated by trapping. Flats with germinating seeds may be protected by 
supporting them on glazed crocks. Such flats must be well away from 
walls and other objects up which the mice can climb and from which they 
can jump onto the flat. Metal screening may also be used to cover the 
flats. 



- 33 - 



MANAGEMENT OF FACILITIES 



The Phytotron Committee sets the policies for the operation of the 
Phytotron. The chairman of the Phytotron Committee is employed full-time 
as a scientist but manages the Phytotron and allocates facilities. The 
maintenance supervisor is responsible for all maintenance and keeps all 
maintenance records. The programmer is responsible for programming all 
facilities and for modifying programs/ for minor maintenance, and for 
replacing and ordering lamps. The greenhouse supervisor is responsible 
for the watering of all plants, preparing pots and soil for seeding, for 
discarding soil and plants from completed experiments, and for keeping 
the Phytotron facilities and the Phytotron area clean and free of mites, 
insects, mice, and diseases. 

Each scientist is responsible for completing a Phytotron Program form 
(see Appendix No. 5) with the following information: the facility 
reguired, the project number and short title, the crop grown, the 
scientist's name and office and home phone numbers, the technician's or 
associate's name and office and home phone numbers, the date the facility 
is required, the estimated time for completion of the experiment, the 
date the facility wa • requested, the scientist's signature, lighting, 
temperature, humidity, and watering instructions, and any special 
instructions. 

Any changes to the program must be in writing on the Shut Down and 
Program Change Request form (Appendix 7). The scientist's and 
technician's names and phone numbers are required so that they can be 
phoned if there is a problem with the growth facility and instructions 
are needed concerning the experiment. 

Scientists are expected to check lights, temperature, and humidity of the 
Phytotron unit they are using throughout the experiment to make sure that 
the conditions are exactly what they requested. The scientist is 
responsible for seeding all pots and for making all observations and 
records of the experiment. 

Each scientist is responsible for filling out a Phytotron Work Order form 
(see Appendix 6) indicating the number, size, and type of pots required, 
the soil mixture or media needed, the type of watering (tap water, 
distilled water or a specific nutrient solution), and the greenhouse or 
plant growth unit in which the pots or flats are to be placed. 

When the experiment has been completed, the scientist fills in the Shut 
Down and Program Change Request form (Appendix 7) and informs the 
greenhouse supervisor of how the material should be disposed. Plants 
infested with insects, infected with disease, or treated with pesticides 
are placed in plastic bags and disposed of in a sanitary landfill, while 
healthy plants and untreated soil are placed in a compost pile. 

All our facilities have routine maintenance at least twice a year (see 
Preventative Maintenance form, Appendix 8). After each experiment the 
unit is thoroughly cleaned and washed prior to the maintenance 
inspection. Three times each week all lights in the phytotron are 
inspected and burnt-out bulbs or ballasts are replaced. A record is kept 
by the maintenance supervisor of all repairs to each plant growth unit. 



- 34 - 



GUIDELINES FOR REPORTING PHYTOTRON EXPERIMENTS 

Plant growth facilities differ in design, maintenance, air flow patterns, 
and other factors which may affect experimental results. Complete and 
accurate interpretation of experimental results is difficult or almost 
impossible if the environment in the plant growth facility is not 
adequately reported. Guidelines for measuring and reporting environmental 
factors in controlled environment facilities have been published by Spomer 
(1980, 1981) and Sager (1982). Our experience suggests the following 
guidelines . 

The guidelines are divided into two categories, those which ought to be 
reported (essential) and those which ideally should be reported 
(desirable). It must be recognized that the measuring equipment and 
available staff will influence which of the additional conditions will be 
measured. However, the preceding discussion of environmental conditions 
should be used as a guide to which of the ideally measured conditions are 
likely to be important. Every effort should be made to measure these, 
and all that deviate greatly from naive expectations ought to be 
reported. These measurements become more important as growing conditions 
deviate from 20 to 25°C, as light intensity becomes high, and as daily 
air temperatures are varied by more than a few degrees C. 



Equipment 

Make and model number of the cabinet or room. 

Temperature (°C) 

ESSENTIAL 

1. Air temperature with a shielded sensor. Specify whether constant 
or variable. If variable, give day and night temperatures and 
specify nominal rate of change from day to night conditions. 

2. If substrate temperature was controlled separately (as in soil 
temperature tanks or with heaters or refrigeration coils), provide 
set or nominal values and a summary of measured values. Note that if 
it was important enough to provide separate temperature control for 
substrate temperature, then values ought to be measured and reported 
for light and dark periods of the daily cycle. 

DESIRABLE 

1. Substrate temperature, if not controlled independently. Measure 
at plant crown level for species with crowns below the soil surface 
or at least at one shallow depth for other species. Summarize 
briefly the results if conditions (air temperature or light) were 
cycled. Check and report in summary form if crop was grown long 
enough to cause shading of the medium by plant canopy. 

2. Leaf temperature. Measure during both the light and dark cycles 
for leaves exposed directly to the light and if relevant for those 
shaded by upper levels of the plant canopy. 



- 35 - 

3. Specify types of temperature sensors employed. 

4. Tolerance limits during normal cycling of equipment. 



Light 

ESSENTIAL 

1. Specify photoperiod and whether change from dark to light period 
was abrupt or gradual. If gradual, indicate how rapidly. State if 
photoperiod and thermoperiod coincide and if not, describe difference, 

2. Types of lamps used. Provide information on type (e.g., 
incandescent, fluorescent, etc.), power rating and voltage applied, 
and phosphor for fluorescent lights. 

3. Light intensity. Measure just above the plant canopy or at 
medium level at seeding time. Any of the three units described above 
may be used but make and model of meter employed should be stated. 
When two light sources were used (e.g., incandescent and cool white 
fluorescent) give data separately for each light source. 



DESIRABLE 

1. Tolerance limits for light intensity. State limits over area of 
plant growth at a specified level. State frequency of monitoring of 
light intensity and deviation from nominal values permitted. 

2. Graph of spectral energy distribution at start of experiment. 
State if this was monitored subsequently and what changes occurred. 



Relative humidity 

ESSENTIAL 

1. Provide day and night values. Describe type of sensor and 
controlling mechanism. 



DESIRABLE 

1. Provide tolerance levels. 

2. Outline any variations associated with daily cycling of the 
cabinet (including those associated with watering) with development 
of the crop or in the crop canopy. 



Carbon dioxide 

ESSENTIAL 

1. State how CO2 levels were controlled. 



- 36 - 



DESIRABLE 

1. Provide data on daily cycling of CO2 levels for a designated 
location in or near the plant canopy. Specify measuring device used. 



Air movement 

DESIRABLE 

1. Indicate if air flow was up, down or horizontal. Specify how and 
where this was measured and provide data. 



Containers, media, and nutrients 

Note: Literature references should be used where appropriate. In the 
absence of such references, all details outlined below should be 
provided. 

ESSENTIAL 

1. Containers. State type of container (wood, plastic, glass, 
clay), color, and inside dimensions. If a hydroponic system was 
used, provide details of construction including information on 
monitoring tests used to ensure proper operation. 

2. Substrate. Include information on amendments and added 
fertilizer. 

3. State how water and nutrients were supplied (e.g., hose, watering 
can, manual hydroponic system, automated hydroponic system, etc.). 

4. Nutrient solutions. If a literature reference cannot be 
supplied, then a complete list of ingredients including 
concentrations must be provided. Frequency of changes of nutrient 
solution, frequency and composition of additions to the nutrient 
solution, and monitoring techniques should be stated where applicable. 

DESIRABLE 

1. If nutrient or water was added manually from a hose or watering 
can, temperature and frequency of added water or nutrient should be 
specified. Indicate quantities applied. State if water or nutrient 
was added directly to the surface of the medium or sprinkled on the 
plant canopy. Monitor substrate and canopy temperature changes 
associated with watering and describe these. 



- 37 - 



REFERENCES AND SUPPLEMENTARY READING 

Althouse, A. D., Turnquist, C. H. and Bracciano, A. F. 1975. Modern 
refrigeration and airconditioning. Goodheart-Willcox Co. Inc., South 
Holland, Illinois. 988 pp. 

Anderson, J. M. 1986. Photoregulation of the composition, function, and 
structure of thylakoid membranes. Ann. Rev. Plant Physiol. 37: 93-136. 

Berry, J. and Bjorkman, 0. 1980. Photosynthetic response and adaptation 
to temperature in higher plants. Ann. .Rev. Plant Physiol. 31: 
491-543. 

Bickford, E. D. and Dunn, S. 1972. Lighting for plant growth. Kent 
State Univ. Press, Kent, Ohio. 221 pp. 

Blackman, F. F. 1905. Optima and limiting factors. Ann. Bot. 19: 
281-295. 

Boodley, J. W. and Sheldrake, R. Jr. 1977. Cornell peat-lite mixes for 
commercial plant growing. New York State College of Agric. and Life 
Sciences. Inf. Bull. No. 43. Cornell University, Ithaca, New York. 



Clayton, R. K. 1970. Light and living matter. Vol. 1. The physical 
part. McGraw-Hill, New York. 

Downs, R. J. 1975. Controlled environments for plant research. 
Columbia Univ. Press, New York. 175 pp. 

Downs, R. J. 1980. Phytotrons. Bot. Rev. 46: 447-489. 

Downs, R. J. and Bailey, W. A. 1967. Control of illumination for plant 
growth. Pp. 635-645 in Wilt, F. H., Wessles, N. K. (eds.). Methods in 
development biology. Thomas Crowell, New York. 

Downs, R. J. and Banaminio, V. P. 1976. Phytotron procedural manual for 
controlled-environmental research at the Southeastern Plant Environment 
Laboratories. North Carolina Agric. Expt. Sta. Tech. Bull. No. 244. 36 
pp. 

Downs, R. J. and Hellmers, H. 1975. Environment and the experimental 
control of plant growth. Academic Press, New York. 145 pp. 

Epstein, E. 1972. Mineral nutrition of plants: principles and 
perspectives. John Wiley, New York. 412 pp. 

Evans, L. T. (ed.) 1963. Environmental control of plant growth. 
Academic Press, New York. 449 pp. 

Federer, C. A. and Tanner, C. B. 1966. Sensors for measuring light 
available for photosynthesis. Ecology 47: 654-657. 



- 38 



Gauch, H. G. 1972. Inorganic plant nutrition. Dowden, Hutchinson and 
Ross, Stroudsburg, Pennsylvania. 488 pp. 

Grace, B. and Hobbs, E. H. 1986. The climate of the Lethbridge 
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(revised) . 39 pp. 

Hatch, M. D., Osmond, C. B. and Slayter, R. 0. 1971. Photosynthesis and 
photorespiration. Proceedings of a conference held at Australian 
National University, Canberra, Australia, Nov. 23-Dec 5, 1970. Wiley 
Interscience, New York. 565 pp. 

Heck, W. W. 1972. Air pollution research on plants in phytotrons. 
NSF-UNESCO-SEPEL Symposium, Durham, North Carolina. 

Hellmers, H. and Hesketh, J. D. 1974. Phytotronics and modelling plant 
growth. Pp. 637-644 in Mechanisms of regulation of plant growth. 
Royal Society of New Zealand, Wellington, New Zealand. 

Hewitt, E. J. 1952. Sand and water culture methods used in the study of 
plant nutrition. Commonwealth Bur. Hort. and Plantation Crops. East 
Mailing, Maidstone, Kent. Tech. Comm. No. 22. Commonwealth Agricultural 
Bureau. 241 pp. 

Hoagland, D. R. 1948. Lectures on the inorganic nutrition of plants. 
Chronica Botanica. Waltham, Massachusetts. 226 pp. 

Hoagland, D. R. and Arnon, D. I. 1950. The water-culture method for 
growing plants without soil. California Agric. Expt. Sta. Circular No. 
347. 32 pp. 

Hudson, J. P. 1957. Control of plant environment. Butterworths, 
London. 240 pp. 

Kozlowski, T. T. (ed.) 1976. Water deficits and plant growth IV. 
Academic Press, New York. 383 pp. 

Kramer, P. J. 1949. Plant and soil water relationships. McGraw Hill, 
New York. 

Lange, 0. L., Nobel, P. S., Osmond, C. B., Ziegler, H. (eds.) 1981. 
Physiological plant ecology. I. Responses to the physical environment. 
Encyclopedia of Plant Physiology. Vol. 12A. Springer-Verlag, New York. 

Langhams, R. W. 1978. A growth chamber manual. Comstock Publishing 
Co., New York. 222 pp. 

Levitt, J. 1972. Responses of plants to environmental stresses. 
Academic Press, New York. 697 pp. 



- 39 - 



LI-COR Inc. 1979. Instrumentation for biological and environmental 
sciences. LI-COR Inc. /LI-COR Ltd., Lincoln, Nebraska. 49 pp. 
(Excerpted from: Advanced Agricultural Instrumentation. Proc. NATO 
Advanced Study Institute on Advanced Agricultural Instrumentation. W. G. 
Gensler, ed. Martinus Nijhoff Publishers, Dordrecht, The Netherlands.) 

Matsumura, S. (ed. ) 1982. Environment-controlled growth rooms in 
Japan. Committee for environment-controlled growth rooms. Faculty of 
Agriculture, University of Tokyo, Tokyo. 67 pp. 

McCree, K. J. 1981. Photosynthetically active radiation. In Lange, 
0. L., Nobel, P. S., Osmond, C. B., Ziegler, H. (eds.) 1981. 
Physiological plant ecology. I. Responses to the physical environment. 
Encyclopedia of Plant Physiology. Vol. 12A. Springer-Verlag, New York. 

Miyayama,H., Funada, S., Kato, M. , Konishi, M. , Matsui, T., Miyagawa, H., 
Terajima, T., and Yamaki, T. (eds.) 1972. Phytotrons and growth 
cabinets in Japan. Japanese Soc. Environment Control in Biology. 
Faculty of Agric, Kyoto University. 93 pp. 

Morse, R. N. 1963. Phytotron design criteria - engineering 
considerations. Pp. 20-37 in Engineering aspects of environment 
control for plant growth. CSIRO, Melbourne, Australia. 

Peacock, J. M. 197 5. Temperature and leaf growth in Lolium perenne. 
II. The site of temperature perception. J. AppI . Ecol. 12: 115-123. 

Piatt, R. B. and Griffiths, J. F. 1964. Environmental measurement and 
interpretation. Reinhold, New York. 235 pp. 

Rees, A. R., Cockshull, K. E., Hand, D. W. and Hurd, R. G. (eds.) 1972. 
Crop processes in controlled environments. International Symposium held 
at the Glasshouse Crops Research Institute, Little Hampton, Sussex, 
England. July, 1971. Academic Press, New York. 

Sager, J. C. 1982. Guidelines for measuring and reporting environmental 
parameters for plant experiments in growth chambers. Paper 82-4056. 
Summer Meeting Amer. Soc. Agric. Engineers, St. Joseph, Michigan. U. of 
Wisconsin-Madison. June 27-30, 1982. 

Seliger, H. H. and McElroy, W. D. 1965. Light: Physical and biological 
action. Academic Press, New York. 

Shropshire, W. Jr. and Mohr, H. (eds.) 1983. Photomorphogenesis. 
Encyclopidia of plant physiology. Vols. 16A and 16B. Springer-Verlag, 
New York. 83 2 pp. 

Slayter, R. 0. 1967. Plant-water relationships. Academic Press, London 
and New York. 366 pp. 

Spomer, L. A. 1980. Guidelines for measuring and reporting environmental 
factors in controlled environment facilities. Commun. Soil Sci . Plant 
Anal. Ill 1203-1208. 



- 40 - 



Spomer, L. A. 1981. Guidelines for measuring and reporting environmental 
factors in growth chambers. Agron. J. 73: 376-378. 

Strain, B. R. (ed.) 1978. Report of the workshop on anticipated plant 
responses to global carbon dioxide enrichment. Duke Environmental 
Centre, Duke University, Durham, North Carolina. 

Tibbitts, T. and Kozlowski, T. K. (eds.) 1979. Controlled environment 
guidelines for plant research. Academic Press, New York. 413 pp. 

Tobin, E. M. and Silverthorne, J. 1985. Light regulation of gene 
expression in higher plants. Ann. Rev. Plant Physiol. 36: 569-593. 

Weast, R. C, Astle, M. J. and Beyer, W. H. (eds.) 1985-86. CRC 
handbook of chemistry and physics. 66 edition. CRC Press. Boca Raton, 
Florida, p. E-41. 

Went, F. W. 1957. The experimental control of plant growth. Chronica 
Botanica, Waltham, Mass. 343 pp. 

Zelitch, I. 1971. Photosynthesis, photorespiration and plant 
productivity. Academic Press, New York and London. 347 pp. 



- 41 - 



APPENDIX 1 



Summary of responsibilities 

General responsibility for Phytotron 

Completing phytotron request form 

Space allocation 

Programming facilities 

Filling pots and watering 

Seeding 

Special soil or seed treatments 

Discarding pots and plants 

Mechanical adjustments 

Changing lights 

Repair and maintenance 

General surveillance of experiment 

Monitoring facilities 

Day 

Night 



Chairman, Phytotron Committee 
Scientist or technician 
Chairman/ Phytotron Committee 
Phytotron staff 
Phytotron staff 
Scientist or technician 
Scientist or technician 
Phytotron staff 
Phytotron staff 
Phytotron staff 
Maintenance supervisor 
Scientist or technician 

Phytotron staff 
Commissionaire 



High Ceiling Rooms 



Soil Tank Rooms 



- 42 - 



APPENDIX 2 



Plant growth rooms 



Propagation Rooms 








Room No. 


Size 


(m) 


L-026 


5.13 


X 


10.77 


L-032 


5.13 


X 


6.71 


L-036 


5.13 


X 


6.71 


L-040 


5.13 


X 


8.97 


L-041 


5.52 


X 


3.83 


L-043 


5.52 


X 


3.83 


L-045 


5.11 


X 


3.66 


L-047 


5.11 


X 


3.66 


L-048 


5.11 


X 


8.64 


L-052 


5.11 


X 


6.71 


L-058 


5.11 


X 


6.71 


L-062 


5.11 


X 


6.71 


L-066 


5.11 


X 


4.11 


SC-15 


5.11 


X 


3.81 


SC-24 


5.08 


X 


4.22 



Area (m^) 



55.25 
34.42 
34.42 
46.02 
21.14 
21.14 
18.70 
18.70 
44.15 
34.29 
34.29 
34.29 
21.00 
19.47 
21.44 



Total 



458.72 



SC-6 
SC-7 
SC-8 
SC-9 



5.05 x 3.35 

5.05 x 3.35 

5.05 x 3.07 

5.05 x 3.35 



16.92 
16.92 
15.50 
16.92 



Total 



66.26 



SC-11 
SC-12 
SC-13 
SC-14 



5.11 x 3.81 

5.11 x 3.81 

5.11 x 3.81 

5.11 x 3.81 



19.47 
19.47 
19.47 
19.47 



Total 



77.88 



TOTAL GROWTH ROOM AREA 



602.86 



- 43 



APPENDIX 3 



Plant growth room benches 



Propagation Room Benches 



Room No. No. Benches 


Bench 


size (m) 


Each 


L-026 


4 


1.42 


X 


5.13 


7.28 


L-032 


2 


1.42 


X 


5.13 


7.28 


L-036 


2 


1.42 


X 


5.13 


7.28 


L-040 


3 


1.42 


X 


5.13 


7.28 


L-041 


1 


1.42 


X 


4.98 


7.07 


L-043 


1 


1.42 


X 


4.98 


7.07 


L-045 


1 


1.12 


X 


5.11 


5.71 


L-047 


1 


1.12 


X 


5.13 


5.75 


L-048 


3 


1.42 


X 


5.11 


7.26 


L-052 


2 


1.42 


X 


5.11 


7.26 


L-058 


2 


1.42 


X 


5.11 


7.26 


L-062 


2 


1.42 


X 


5.11 


7.26 


L-066 


1 


1.42 


X 


5.11 


7.26 


SC-15 


2 


1.45 


X 


5.05 


7.32 


SC-24 


2 


1.09 


X 


5.08 


5.54 



Bench area (m 2 ) 

Total 



29.12 

14.56 

14.56 

31.84 

7.07 

7.07 

5.71 

5.75 

21.78 

14.52 

14.52 

14.52 

7.26 

14.64 

11.08 



Total 



204.00 



High Ceiling Room Benches 



SC-6 
SC-7 
SC-8 
SC-9 



2 


1.30 x 5.05 


6.57 


2 


1.30 x 5.05 


6.57 


2 


1.30 x 5.05 


6.57 


2 


1.30 x 5.05 


6.57 



Total 



13.14 
13.14 
13.14 
13.14 

52.56 



Soil Tank Room Benches 



SC-11 


2 


1.45 x 5.05 


7.32 


SC-12 


2 


1.45 x 5 05 


7.32 


SC-13 


2 


1.45 x 5.05 


7.32 


SC-13 


2 


1.45 x 5.05 


7.32 



Total 
TOTAL PLANT GROWTH AREA 



14.64 
14.64 
14.64 
14.64 

58.56 

315.12 



- 44 



APPENDIX 4 



Experimental rooms with limited light 



Room No. Temp. (°C) 

SC-16D 25 

SC-16F 20 

SC-16B 15 

SC-16E 10 
SC-16C 5 

SE-14 5 

SE-15 5 

SE-11 5 

SE-1 3 

SE-16 2.5 

SE-10 .75 

SC-16A .5 

SC-17F -3 

SC-17E -5 

SC-17D -10 

SC-17A -15 

SC-17B -20 

SC-18A -20 

SC-18B -40 

SC-23B -40 

SE-2 -40 
SC-17C -20 to +25 
SC-23A -20 to +25 



Size 


(m) 


Area (m 2 ) 


2.79 


X 


1.83 


5.11 


2.79 


X 


1.83 


5.11 


2.79 


X 


1.83 


5.11 


2.79 


X 


1.83 


5.11 


2.79 


X 


1.83 


5.11 


3.01 


X 


2.01 


6.13 


3.01 


X 


2.01 


6.13 


2.44 


X 


1.83 


4.47 


5.00 


X 


3.91 


19.55 


3.01 


X 


2.01 


6.13 


2.44 


X 


1.91 


4.66 


2.79 


X 


1.83 


5.11 


2.79 


X 


1.83 


5.11 


2.79 


X 


1.83 


5.11 


2.79 


X 


1.83 


5.11 


2.79 


X 


1.83 


5.11 


2.79 


X 


1.83 


5.11 


5.72 


X 


1.83 


10.47 


3.76 


X 


1.68 


6.32 


3.35 


X 


3.66 


12.26 


3.66 


X 


2.97 


10.87 


2.79 


X 


1.83 


5.11 


2.39 


X 


2.08 


4.97 



- 45 - 
APPENDIX 5 

PHYTOTRON PROGRAM FORM 



COMPLETE SECTIONS: 1-2-3 



fXl ALL APPROPRIATE BOXES 



SECTION "1" 

CABINET REQUIRED # _ 

TITLE OF EXPERIMENT 

SCIENTIST: 

PHONE: 



CROP 



PROJECT # 



(OFFICE) 



ALTERNATE: 
PHONE: 



(HOME) 



(OFFICE 



(HOME) 



SECTION "2" IN THE EVENT OF CABINET MALFUNCTION - AFTER 4:30 PM AND WEEKENDS 

\ZD 1) NOTIFY SCIENTIST CH IF NO ONE CAN BE REACHED: EZI - SHUTDOWN UNTIL SCIENTIST 
NOTIFY ALTERNATE LJ CAN BE REACHED 

I I - CALL MAINTENANCE STAFF 
IN 

| I - SHUTDOWN TILL NEXT 
WORKING DAY 



I 1 2) SHUTDOWN AND CALL MAINTENANCE STAFF IMMEDIATELY 
I I 3) SHUTDOWN UNTIL NEXT WORKING DAY 



SECTION "3" 



WATERING 
NUTRIENT 
PESTICIDE 
OTHER 



SECTION "4" FOR PROGRAMMER USE ONLY 



1 




















































2 




















































3 




















































TEMP. 
TIME 


24 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


13 


14 


15 


16 


17 


18 


19 


20 


21 


22 


23 


24 



SECTION "5" - PROGRAM INSTRUCTIONS 

1) LIGHTING: FLUORESCENT COOL WHITE EZ1 INCANDESCENT BULBS EZ1 

FLUORESCENT GROW LUX WS I i NO INCANDESCENT BULBS LZZI 

2) LIGHTS ON AM | | PM | [ 

LIGHT INTENSITY 1/3 I I 2/3 | | FULL | I 

LIGHTS ON AM I | PM | | 



'NOTE - ANY FURTHER LIGHTING INSTRUCTIONS LIST ON REVERSE SIDE. 



3) TEMPERATURE: DAY 
NIGHT 



'NOTE - ANY FURTHER TEMPERATURE INSTRUCTIONS LIST ON REVERSE SIDE. 



4) RELATIVE HUMIDITY: DAY 1 

NIGHT 1 

***NOTE - ANY FURTHER INSTRUCTIONS LIST ON REVERSE SIDE. 

5) DATE EXPERIMENT WILL ENTER CABINET 

♦""ATTENTION: NO PROGRAMMING ONE DAY BEFORE A HOLIDAY 



MINIMUM OF FIVE WORKING DAYS NOTICE FOR START-UPS, IN ADVANCE 



DATE: 



SIGNATURE: 



- 46 - 



APPENDIX 6 

AGRICULTURE CANADA RESEARCH STATION 
Lethbridge, Alberta TlJ 4B1 



PHYTOTRON WORK ORDER 



Work Order No. 



Date requested^ 
Date required 



Requested by 

Section: AS CE PP PS SS VM ADA 

Phone No. 



Location: Greenhouse No. 
Other 



GC No. 



GR No. 



PR No. 



work required: ALLOW 7 WORKING DAYS FOR COMPLETION OF ORDER 

Containers filled: Type and Size 

Soil Mixture (ratio) : Soil 
Special (specify) 



Number 



Sand 



Peat Moss 



Manure 



Containers emptied: No. 
Pest Control: Type 



To Compost Pile 



Treatment 



City Dump 



Other: 



Priority 
Notes 



(Greenhouse Use Only) 
Date started Date Completed 



By 



Greenhouseman 



Requested by 



ACKNOWLEDGEMENT 



Work Order No. 
Date order received 



Expected completion date as requested 



or 



Date 



By 



Greenhouseman 



- 47 - 

APPENDIX 7 
SHUT-DOHN AND PROGRAM CHANGE REQUEST 



UNIT # 



COMPLETE ONLY THOSE SECTIONS WHICH PERTAIN TO YOUR NEEDS: [X] ALL APPROPRIATE BOXES 



SECTION "1" 



SHUT-DOWN □ 

DATE ACTION REQUIRED 

CLEAN UNIT 



I WILL NOT BE REUSING THIS CABINET ... □ 

I WILL BE USING THIS CABINET AGAIN ... □ DATE OF RE-USE 



SECTION "2" 



CHANGE: LIGHT INTENSITY - OFF 

- 1/3 

- 2/3 

- FULL 
OTHER INSTRUCTIONS: 



DATE ACTION REQUIRED 



SECTION "3" 

CHANGE: TEMPERATURE - NEW TEMPERATURE; DATE ACTION REQUIRED 



OTHER INSTRUCTIONS: 



SECTION "4" 

CHANGE: RELATIVE HUMIDITY - NEW SETTING; DATE ACTION REQUIRED 



OTHER INSTRUCTIONS: 



*****ATTENTION - FOR ANY CHANGE IN DAYLIGHT DURATION OR THE START OF A NEW EXPERIMENT A 
NEW PROGRAM MUST BE SUBMITTED. 



SIGNATURE: 



DATE SUBMITTED: 



- 48 - 

APPENDIX 8 
PREVENTATIVE MAINTENANCE 



t ***FOR GREENHOUSE AND MAINTENANCE USE ONLY' 



THIS CABINET WILL BE READY FOR RE-USE ON (DATE) 



THIS CABINET WAS CLEANED AND READY FOR RE-USE (DATE) _ 
SIGNATURE: DATE: 



THIS CABINET IS ON TEST DATE: 



SIGNATURE: 



TEMPERATURE SETTING: 



IN THE EVENT OF A MALFUNCTION 1) call Carey Jackson (Maintenance - 395 or page) 

2) after hours - call C. Jackson @ 345-2393 

- if no answer, shut cabinet down and 
indicate on commissionaire's report 



Start-Up 



Unit/Room No.: 

Previous temp.: 

New temp, required: 

Humidity required: 

Change reason: 

High limit set I | 

Low limit set I j 

Computer center notified . . | | 

Audible alarm on | | 

Circuit breakers/fuses .... | | 

Circulation fans | | 

Aspirator fan | | 

Light switches set | ] 



Date: 



Lights required: 
Heaters required: 



Heater switches set | | 

Temperature/humidity recorder | | 

Temperature program timer set | | 

Humidity program timer set | | 

Defrost limit set (max +7°C) I I 

Dampers on correct coil | I 

Top defrost heater limit set (max. +10°C) I I 

Bottom defrost heater limit set (max. +10°C) ... | I 

Pilot lights operating | | 



- 49 - 



APPENDIX 9A 



Long-term averages and extremes of air temperature (°C), 1902-1985, 
Lethb ridge 







Mean 






Extreme 






Month 


Max 


Min 


Daily 


Max 


Year 




Min 


Year 


January 


-3.0 


-15.1 


-9.0 


17.8 


1931 




-43.0 


1909 


February 


-0.4 


-12.7 


-6.6 


19.7 


1962 




-42.2 


1905 


March 


4.3 


-8.3 


-2.0 


24.4 


1906,66 




-37.8 


1947 


April 


12.4 


-1.6 


5.3 


33.7 


1906 




-27.2 


1940 


May 


17.7 


3.6 


10.6 


33.3 


1928 




-12.8 


1954 


June 


21.6 


7.9 


14.8 


35.6 


1933,36 




-3.3 


1951 


July 


26.0 


10.3 


18.1 


39.1 


1904 




0.8 


1910 


August 


24.9 


9.1 


17.0 


37.2 


1906 




-1.4 


1911 


September 


19.2 


4.6 


12.0 


35.8 


1950 




-15.6 


1934 


October 


13.9 


0.0 


7.0 


30.0 


1904,33, 


.80 


-26.1 


1919 


November 


5.2 


-6.9 


-0.8 


23.1 


1908,40, 


.49 


-35.6 


1912 


December 


-0.3 


-11.7 


-6.0 


19.6 


1908 




-42.5 


1924 


Annual 


11.8 


-1.7 


5.0 


39.1 






-43.0 





APPENDIX 9B 



Frost data, 1902-1985, Lethbridge 



Extremes 



Average Earliest 



Latest 



Last frost in spring (0°C) 
First frost in fall (0°C) 
No. of frost-free days 



May 1 
Sep 15 
117 



Apr 26 1940 

Aug 14 1928 

80 (1951) 



Jul 3 1979 
Oct 14 1928 
171 (1940) 



Last killing frost in spring (-2°C) May 7 Jun 2 1984 

First killing frost in fall (-2°C) Sep 25 Sep 3 1962 Oct 22 1984 
No. of crop days 140 110 (1921) 178 (1940) 



- 50 - 



APPENDIX 9C 



20-| 



15- 



O 

o 

w 10 

oc 

£ 5 

Q. 
111 



o 



0- 



-5- 



-10 




1 1 1 1 — 

JAN FEB MAR APR MAY 



JUN 



JUL AUG SEP OCT NOV DEC 



Mean soil temperature at three depths, 1967-1985, 
Lethbridge 



APPENDIX 9D 



Average monthly growing degree-days, heating 
degree-days, and corn heat units in the Lethbridge area 











Heating 






G 


rowing 




degree-days 


Corn 




degree 


-days 


above 


below 


heat 




5°C 


and 


10°C 


18°C 


units 


January 


1 







851 





February 


4 







666 





March 


8 







634 





April 


45 




9 


383 





May 


159 




60 


221 


308 


June 


273 




141 


106 


518 


July 


369 




240 


29 


658 


August 


337 




204 


48 


616 


September 


194 




93 


168 





October 


83 




25 


323 





November 


12 




2 


560 





December 


2 







729 






Total 



1487 



774 



4718 



- 51 - 



APPENDIX 9E 



Long-term averages and extremes of precipitation and snowfall, 1902-1985, 
Lethb ridge 









Greatest 


Least 


Greatest 








precipi 


tation 


precip: 


Ltation 


snowf a 


11 








(mm) 


(mm) 


(cm) 




Month 


Mean 


Median 


Amount 


Year 


Amount 


Year 


Amount 


Year 


Jan 


19.3 


18.0 


50.7 


1978 


0.3 


1931 


66.1 


1978 


Feb 


17.1 


17.1 


55.1 


1953 


0.5 


1977 


55.1 


1953 


Mar 


23.9 


22.2 


63.8 


1933 


2.5 


1917 


63.8 


1933 


Apr 


32.4 


27.5 


112.5 


1967 


0.5 


1902 


136.9 


1967 


May 


54.6 


41.7 


286.3 


1902 


2.3 


1928 


66.3 


1903 


Jun 


72.4 


64.5 


207.5 


1953 


2.0 


1985 


20.3 


1951 


Jul 


41.6 


35.1 


151.1 


1902 


1.5 


1967 


1.0 


1914 


Aug 


41.2 


32.1 


168.1 


1978 


1.5 


1969 


trace 


1952 


Sep 


41.2 


31.4 


123.4 


1925 


0.0 


1948 


69.3 


1968 


Oct 


22.6 


17.5 


111.0 


1946 


0.0 


1944 


62.0 


1933 


Nov 


18.6 


14.0 


73.2 


1927 


0.0 


1917 


73.2 


1927 


Dec 


19.0 


16.5 


57.7 


1933 


0.0 


1913 


57.7 


1933 



Total 



403.9 



Extremes 



709.1 



1902 



193.8 



1918 



305.6 



1933 



APPENDIX 9F 



Percent probability of growing season rainfall, Lethbridge 





Mean 


P: 


robabil 


ities 


of receiving 


amounts (mm) 


greater than 


Month 


10 


20 


30 


40 


50 


60 


70 


80 


90 


100 


Mar 


23.9 


85 


57 


23 


12 


6 


1 










Apr 


32.4 


85 


63 


43 


24 


18 


17 


9 


6 


4 


2 


May 


55.3 


98 


88 


71 


55 


37 


32 


26 


21 


16 


11 


Jun 


73.5 


99 


91 


82 


68 


60 


55 


45 


41 


33 


27 


Jul 


42.1 


94 


74 


56 


44 


34 


26 


18 


12 


7 


4 


Aug 


41.0 


85 


70 


52 


41 


33 


24 


17 


11 


10 


5 



- 52 



APPENDIX 9G 



Lethbridge sunshine data, 1909-1985 









Maximum 


Minimum 




Mean 


Pp rppnt" 












daily 


-L C J- \_ t; 11 I* 

of 


Hours/ 




Hours/ 






hours 


possible 


month 


Year 


month 


Year 


Jan 


3.2 


36 


143 


1985 


43 


1971 


Feb 


4.3 


43 


173 


1931 


74 


1940 


Mar 


5.2 


45 


231 


1912 


90 


1983 


Apr 


6.9 


50 


283 


1934 


103 


1920 


May 


8.4 


54 


344 


1928 


136 


1927 


Jun 


9.3 


57 


385 


1917 


207 


1942 


Jul 


11.0 


70 


406 


1933 


251 


1912 


Aug 


9.7 


68 


392 


1969 


220 


1968 


Sep 


7.0 


56 


283 


1938 


114 


1985 


Oct 


5.5 


51 


231 


1952 


101 


1951 


Nov 


3.8 


41 


178 


1917 


61 


1927 


Dec 


3.0 


37 


156 


1913 


45 


1980 



Annual extremes 



2593 



1943 



2120 



1942 



APPENDIX 10 



Standard Abbreviations 



Celsius degree 


°C 


meter 


m 


centimeter 


cm 


metric ton 


t 


cubic centimeter 


cm^ 


micron 


urn 


cubic meter 


m3 


microEinstein 


UE 


gram 


g 


milligram 


mg 


hectolux 


hlx 


milliliter 


ml 


kilogram 


kg 


millimeter 


mm 


kilolux 


klx 


milliwatt 


mW 


kilometer 


km 


nanometer 


nm 


Langley 


Ly 


square centimeter 


cm 


liter 


1 


square meter 


m 2 


lux 


lx 


watt 


W 



- 53 - 



APPENDIX 11 



Conversion factors 
To Convert From* 



To 



Multiply By 



Acres 

Cubic feet/min 

Cubic feet/min 

Cubic inch 

Cubic yard 

Fathom 

Feet/min 

Feet/min 

Firkin 

Foot candle 

Furlong 

Gallons/min 

Hectare 

Inch 

Langley/min 

Langley/min 

Meters/sec 

Mile/hr 

Mile/hr 

Ounce (avdp) 

Ounce (U. S. Fluid) 

Pound (avdp) 

Pound/in 2 

Pound/in 2 

Pound/ft 2 

Pound/ft 3 

Quart (U. S. Liq. ) 

Scruple 

Square foot 

Square yard 

Ton of regrigeration 

(U. S. Comm.) 

Ton of refrigeration 

Ton (metric) 

Ton (short) = 2000 lb 

Yard 

Watt/cm 2 

Watt/cm 2 

Watt/cm 2 



hectares 

m 3 min~l 

liters min~l 

cm 3 

m3 

m 

m min 



-1 
.-1 



m sec 

liters 

lux 

m 

liters min~l 

m 2 

cm 

cal cm~ 2 min - ^ 



mw cm 



-2 



-2 

m min~l 
km hr~l 
m min~l 

g 

ml 

g 

mm Hg 
g cm 
kg m -2 
kg m~ 3 
liters 

g 

m 2 
m 2 

Btu hr" 1 

kg cal hr - -'- 

kg 

kg 

m 

cal cm -2 min - -*- 



0. 

0. 
28. 
16. 

0. 

1. 

0. 

0. 

34, 

10. 

201, 

3, 
10,000 

2, 

1 
69, 
60, 

1, 
26, 
28, 
29, 
453, 
51, 
70, 

4, 
16 

0, 

1, 

0, 

0, 



404 

0283 

3 

387 

764 

8 

3048 

0051 

1 

76 

2 

78 

54 

7 

6 

8 

35 

57 

6 

7 

3 

88 

946 
3 

0929 
836 



Joule sec 



-1 



cm 



-2 



erg sec - -*- cm -2 



12,000 
3023.95 
1000 
907.18 
0.914 
14.34 
1 
1 x 10' 



*To facilitate conversion, the time units are those customarily used 
in the past with the f. p. s. system; i.e., feet per min. x .3048 
would convert to meters per minute in preference to m/sec. 



(From Downs and Bonaminio 1976) 



- 54 - 

APPENDIX 12 

Cornell mix 

Make up in bushel tubs (35.2 liter) 

Add in proportion by volume 
2 parts peat moss 

2 parts No. 3 grade (medium) vermiculite 
1 part sand 

To each tub add: 
165 g CaC0 3 

38 g 0-45-0 fertilizer 
150 g Osmocote 18-6-12 

1 g 300 FE sequestrene 

2 g fritted trace elements 

(Adapted from Boodley and Sheldrake 1977) 

APPENDIX 13 
Hoagland's no. 1 nutrient solution 



All chemicals dissolved in distilled water. 
Nutrient is made up in 20 liter plastic carboys. 



Add 



Approximately 10 liters of distilled water 

17 ml 1 M KH 2 P0 3 

17 ml Micronutrient solution* 

33 ml 1 M MgS0 4 

81 ml 1 M KN0 3 

81 ml 1 M Ca(N0 3 ) 2 

1.35 g Iron citrate dissolved by heating in approximately 1 liter 

distilled water 
Distilled water to make up to 20 liters 



*Micronutrient solution 
1 liter contains 
2.86 g boric acid (H3BO3) 
1.81 g manganese chloride (MnCl2 • 4H 2 0) 
0.22 g zinc sulphate (ZnS0 4 • 7H 2 0) 
0.08 g copper sulphate (CuS0 4 • 5H 2 0) 
0.02 g molybdic acid (H 2 Mo0 4 • H 2 0) 



(Adapted from Hoagland and Arnon 1950) 



- 55 - 



APPENDIX 14 



CONVERSION OF UNITS 



Conversion of Photon Units to Radiometric Units 

Conversion of quantum sensor output in ^E s' 1 nr 2 (400-700 nm) to 
radiometric units in W nr 2 (400-700 nm) is complicated. The conversion 
factor will be different for each light source, and the spectral distribution 
curve of the radiant output of the source (W\ ; W nr 2 nm 1 ) must be known 
in order to make the conversion. The accurate measurement of W\ is a 
difficult task, which should not be attempted without adequate equipment 
and calibration facilities. The radiometric quantity desired is the integral of 
Vv\ over the 400-700 nm range, or: 



Wj 



W x d\ 



At a given wavelength X, the number of photons per second is 



photons s = 



hc/X 



(1) 



(2) 



where h = 6.63 • 10 -34 joule-s (Planck's constant), c = 3.00 • 10 8 m s -1 
(velocity of light) and X is in nm. hc/X is the energy of one photon. Then, 
the total number of photons per second in the 400-700 nm range is 



f 

J40i 



w x 
hc/x 



dA 



0) 



This is the integral which is measured by the sensor. If ft is the reading of 
the quantum sensor in ^E s 1 nr 2 (1 /iE s -1 nr 2 ■ 6.022 • 10 17 photons s" 1 
m" 2 ), then 



— dx 

•oo L,_/ v 



hc/X 
Combining Eq. (1) and Eq. (4) gives 



W T = 6.022 • 10 17 (Rhc) 



10 17 (Rhc) J -? 



W x dx 



f 

J 401 



(4) 



(5) 



XW X dX 



To achieve the two integrals, discrete summations are necessary. Also, 
since W x appears in both the numerator and the denominator, the nor- 
malized curve N x may be substituted for it. Then 



2 N X ^X 



W T = 6.022- 10 17 (Rhc) 



2 X ^£ X 



(6) 



where AX is any desired wavelength interval, Xj is the center wavelength 
of the interval and Nxj is the normalized radiant output of the source at the 
center wavelength. In final form this becomes 



W T = 119.8 (R) 



2 N M 

2 *% 



W nr 



(7) 



where R is the reading in /xE s -1 nr 2 . 

The following procedure should be used in conjunction with Eq. (7). 

1. Divide the 400-700 nm range in i' intervals of equal wavelength spac- 
ing AX. 

2. Determine the center wavelength (Xj) of each interval. 

3. Determine the normalized radiant output of the source (Nx,) at each of 
the center wavelengths. 

4. Sum the normalized radiant outputs as determined in Step 3 to find 

5. Multiply the center wavelength by the normalized radiant output at that 
wavelength for each interval. 

6. Sum the products determined in Step 5 to find IXjNx:. 

i ' 

7. Use Eq. (7) to find Wj in W nr 2 , where R is the quantum sensor out- 
put in fit s' 1 nr 2 . 



The following approximation assumes a flat spectral distribution curve of 
the source over the 400-700 nm range (equal spectral irradiance over the 
400-700 nm range) and is shown as an example. 

Given: i = 1 

AX = 300 nm 
.Xj = 550 nm 

WT - «" (R> ( Z^f^ ) = 2%P = 022(H) W m- 2 
1 550 • N (550) 550 



1 w nr 2 - 4.6 mE s -1 nr 2 

This conversion factor is within ±8.5% of the factors determined by 
McCree as listed in Table I (8). 

Conversion of Photon Units to Photometric Units 

To convert photon units (/xE s" 1 nr 2 , 400-700 nm) to photometric units 
(lux 400-700 nm), use the above procedure, except 

a) Replace Eq. (1) with 



•X 



Lux = 683 J«. yxw x dx 

where yx is the luminosity coefficient of the standard CIE curve with 
yx = 1 at 550 nm and Wx is the spectral irradiance (W nr 2 nm 1 ). 

b) Replace Eq. (5) with 
Lux = (683) 



r too 

J yx Wx dx 

(6.022 • 10 17 ) (Rhc) J ~/ X 

L xw ^ 

c) Replace Eq. (6) with 

2 v Xj N Xi AX 
Lux = (683) (6.022 • 10 17 ) (Rhc) 

2 x i N X| AX 

i 

d) Replace Eq. (7) with 

2 v Xj Nxj 
Lux = 8.17- 10*(R)-!- 



2 xN Xi 



e) Replace Step 4 with: 

4a) Multiply the luminosity coefficient (yx) of the center wavelength by 
the normalized radiant output (N K ) at that wavelength for each 
interval. 

4b) Sum the products determined in Step 4a to find I yx; Nx:. 

i ' ' 

The following approximation assumes a flat spectral distribution curve of 
the source over the 400-700 nm range (equal spectral irradiance over the 
400-700 nm range) and is shown as an example. 

Given: i = 1 to 31 

AX = 10 nm 

X,= 400, X 2 = 410, X 3 = 420 X 31 = 700 

Nx = 1 for all wavelengths 

yx, = 0.0004, yx 2 = 0.0012, yX 3 = 0.004 yx 3 , = 0.0041 



2 y Xj 



Lux = 8.17- 10«(R)-!. = 8.17.10 4 (R)(-^T-) 



Or, 



2 x i 

Lux = 51.2 R, where R is in ^E s 1 nr 2 
1000 lux = '1 klux = 19.5 mE s" 1 nr 2 



17050 



(From LI-COR 1979) 



- 56 - 



Top left. The main floor phytotron at the 
Lethbridge Research Station. 
Top right. Examining plant in a 
virus-vector chamber. 

Middle left. Barley growing in cylinders 
of soil. 

Middle right. Mature wheat in a 
propagation room. 

Bottom left. Corn in a high-ceiling 
growth chamber. 

Bottom right. Pollinating wheat in a 
propagation room. 



CANADIAN AGRI 




BIBLIOTHEQUE CANADIENNE DE I'AGRICULTURE 

3 TD73 0011fl072 D